

<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://www.flex-pharma.com/role/AccruedExpensesAndOtherCurrentLiabilities" xlink:href="flks-20161231.xsd#AccruedExpensesAndOtherCurrentLiabilities" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/AccruedExpensesAndOtherCurrentLiabilitiesDetails" xlink:href="flks-20161231.xsd#AccruedExpensesAndOtherCurrentLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/AccruedExpensesAndOtherCurrentLiabilitiesTables" xlink:href="flks-20161231.xsd#AccruedExpensesAndOtherCurrentLiabilitiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CashEquivalentsAndMarketableSecurities" xlink:href="flks-20161231.xsd#CashEquivalentsAndMarketableSecurities" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CashEquivalentsAndMarketableSecuritiesDetails" xlink:href="flks-20161231.xsd#CashEquivalentsAndMarketableSecuritiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CashEquivalentsAndMarketableSecuritiesTables" xlink:href="flks-20161231.xsd#CashEquivalentsAndMarketableSecuritiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CommitmentsAndContingencies" xlink:href="flks-20161231.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CommitmentsAndContingenciesMinimumFutureLeasePaymentsDetails" xlink:href="flks-20161231.xsd#CommitmentsAndContingenciesMinimumFutureLeasePaymentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CommitmentsAndContingenciesNarrativeDetails" xlink:href="flks-20161231.xsd#CommitmentsAndContingenciesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CommitmentsAndContingenciesTables" xlink:href="flks-20161231.xsd#CommitmentsAndContingenciesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CommonStock" xlink:href="flks-20161231.xsd#CommonStock" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CommonStockNarrativeDetails" xlink:href="flks-20161231.xsd#CommonStockNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CommonStockRestrictedCommonStockActivityDetails" xlink:href="flks-20161231.xsd#CommonStockRestrictedCommonStockActivityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CommonStockSharesReservedForFutureIssuanceDetails" xlink:href="flks-20161231.xsd#CommonStockSharesReservedForFutureIssuanceDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/CommonStockTables" xlink:href="flks-20161231.xsd#CommonStockTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/ConsolidatedBalanceSheetParenthetical" xlink:href="flks-20161231.xsd#ConsolidatedBalanceSheetParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/ConsolidatedBalanceSheets" xlink:href="flks-20161231.xsd#ConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/ConsolidatedStatementOfCashFlows" xlink:href="flks-20161231.xsd#ConsolidatedStatementOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/ConsolidatedStatementOfConvertiblePreferredStockAndStockholdersEquityDeficit" xlink:href="flks-20161231.xsd#ConsolidatedStatementOfConvertiblePreferredStockAndStockholdersEquityDeficit" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/ConsolidatedStatementOfConvertiblePreferredStockAndStockholdersEquityDeficitParenthetical" xlink:href="flks-20161231.xsd#ConsolidatedStatementOfConvertiblePreferredStockAndStockholdersEquityDeficitParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/ConsolidatedStatementOfOperations" xlink:href="flks-20161231.xsd#ConsolidatedStatementOfOperations" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/ConsolidatedStatementsOfComprehensiveLoss" xlink:href="flks-20161231.xsd#ConsolidatedStatementsOfComprehensiveLoss" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/ConvertiblePreferredStock" xlink:href="flks-20161231.xsd#ConvertiblePreferredStock" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/ConvertiblePreferredStockNarrativeDetails" xlink:href="flks-20161231.xsd#ConvertiblePreferredStockNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/DocumentAndEntityInformation" xlink:href="flks-20161231.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/FairValueMeasurements" xlink:href="flks-20161231.xsd#FairValueMeasurements" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/FairValueMeasurementsDetails" xlink:href="flks-20161231.xsd#FairValueMeasurementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/FairValueMeasurementsTables" xlink:href="flks-20161231.xsd#FairValueMeasurementsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/IncomeTaxes" xlink:href="flks-20161231.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/IncomeTaxesNarrativeDetails" xlink:href="flks-20161231.xsd#IncomeTaxesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/IncomeTaxesScheduleOfDeferredTaxAssetsAndLiabilitiesDetails" xlink:href="flks-20161231.xsd#IncomeTaxesScheduleOfDeferredTaxAssetsAndLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/IncomeTaxesScheduleOfEffectiveIncomeTaxRateReconciliationDetails" xlink:href="flks-20161231.xsd#IncomeTaxesScheduleOfEffectiveIncomeTaxRateReconciliationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/IncomeTaxesTables" xlink:href="flks-20161231.xsd#IncomeTaxesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/Inventory" xlink:href="flks-20161231.xsd#Inventory" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/InventoryDetails" xlink:href="flks-20161231.xsd#InventoryDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/InventoryTables" xlink:href="flks-20161231.xsd#InventoryTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/NetLossPerShare" xlink:href="flks-20161231.xsd#NetLossPerShare" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/NetLossPerShareDetails" xlink:href="flks-20161231.xsd#NetLossPerShareDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/NetLossPerShareTables" xlink:href="flks-20161231.xsd#NetLossPerShareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/OrganizationAndOperations" xlink:href="flks-20161231.xsd#OrganizationAndOperations" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/OrganizationAndOperationsDetails" xlink:href="flks-20161231.xsd#OrganizationAndOperationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/PropertyAndEquipmentNet" xlink:href="flks-20161231.xsd#PropertyAndEquipmentNet" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/PropertyAndEquipmentNetDetails" xlink:href="flks-20161231.xsd#PropertyAndEquipmentNetDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/PropertyAndEquipmentNetTables" xlink:href="flks-20161231.xsd#PropertyAndEquipmentNetTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/QuarterlyFinancialInformationUnaudited" xlink:href="flks-20161231.xsd#QuarterlyFinancialInformationUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/QuarterlyFinancialInformationUnauditedDetails" xlink:href="flks-20161231.xsd#QuarterlyFinancialInformationUnauditedDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/QuarterlyFinancialInformationUnauditedTables" xlink:href="flks-20161231.xsd#QuarterlyFinancialInformationUnauditedTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/RelatedParties" xlink:href="flks-20161231.xsd#RelatedParties" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/RelatedPartiesDetails" xlink:href="flks-20161231.xsd#RelatedPartiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/RestrictedCash" xlink:href="flks-20161231.xsd#RestrictedCash" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/RestrictedCashDetails" xlink:href="flks-20161231.xsd#RestrictedCashDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SegmentInformation" xlink:href="flks-20161231.xsd#SegmentInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SegmentInformationDetails" xlink:href="flks-20161231.xsd#SegmentInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SegmentInformationTables" xlink:href="flks-20161231.xsd#SegmentInformationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/StockBasedCompensation" xlink:href="flks-20161231.xsd#StockBasedCompensation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/StockBasedCompensationNarrativeDetails" xlink:href="flks-20161231.xsd#StockBasedCompensationNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/StockBasedCompensationScheduleOfFairValueAssumptionsDetails" xlink:href="flks-20161231.xsd#StockBasedCompensationScheduleOfFairValueAssumptionsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/StockBasedCompensationSummaryOfStockBasedCompensationExpenseDetails" xlink:href="flks-20161231.xsd#StockBasedCompensationSummaryOfStockBasedCompensationExpenseDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/StockBasedCompensationSummaryOfStockOptionActivityDetails" xlink:href="flks-20161231.xsd#StockBasedCompensationSummaryOfStockOptionActivityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/StockBasedCompensationTables" xlink:href="flks-20161231.xsd#StockBasedCompensationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SubsequentEvents" xlink:href="flks-20161231.xsd#SubsequentEvents" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SubsequentEventsDetails" xlink:href="flks-20161231.xsd#SubsequentEventsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPolicies" xlink:href="flks-20161231.xsd#SummaryOfSignificantAccountingPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPoliciesDepreciationOverEstimatedUsefulLifeDetails" xlink:href="flks-20161231.xsd#SummaryOfSignificantAccountingPoliciesDepreciationOverEstimatedUsefulLifeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPoliciesNarrativeDetails" xlink:href="flks-20161231.xsd#SummaryOfSignificantAccountingPoliciesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:href="flks-20161231.xsd#SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfChangesInAccumulatedOtherComprehensiveLossDetails" xlink:href="flks-20161231.xsd#SummaryOfSignificantAccountingPoliciesSummaryOfChangesInAccumulatedOtherComprehensiveLossDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:href="flks-20161231.xsd#SummaryOfSignificantAccountingPoliciesTables" xlink:type="simple" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/AccruedExpensesAndOtherCurrentLiabilities" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/AccruedExpensesAndOtherCurrentLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:href="flks-20161231.xsd#flks_AccruedExpensesAndOtherCurrentLiabilities" xlink:label="loc_flks_AccruedExpensesAndOtherCurrentLiabilities_24662f6f-e2d4-11e3-5ec9-d3760d571408" xlink:type="locator" />
    <link:loc xlink:href="flks-20161231.xsd#flks_AccruedResearchAndDevelopmentExpenseCurrent" xlink:label="loc_flks_AccruedResearchAndDevelopmentExpenseCurrent_9fb53d92-fb67-1459-d265-d3760d56bf35" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_flks_AccruedExpensesAndOtherCurrentLiabilities_24662f6f-e2d4-11e3-5ec9-d3760d571408" xlink:to="loc_flks_AccruedResearchAndDevelopmentExpenseCurrent_9fb53d92-fb67-1459-d265-d3760d56bf35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccruedProfessionalFeesCurrent" xlink:label="loc_us-gaap_AccruedProfessionalFeesCurrent_4ed680eb-fff6-d6ed-0239-7b9bb87e111b" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_flks_AccruedExpensesAndOtherCurrentLiabilities_24662f6f-e2d4-11e3-5ec9-d3760d571408" xlink:to="loc_us-gaap_AccruedProfessionalFeesCurrent_4ed680eb-fff6-d6ed-0239-7b9bb87e111b" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_e20e4396-1ab7-d9ec-b779-e1a72ae620da" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_flks_AccruedExpensesAndOtherCurrentLiabilities_24662f6f-e2d4-11e3-5ec9-d3760d571408" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_e20e4396-1ab7-d9ec-b779-e1a72ae620da" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccruedMarketingCostsCurrent" xlink:label="loc_us-gaap_AccruedMarketingCostsCurrent_073466e9-e2be-e4b0-bf7c-3c1e90be2873" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_flks_AccruedExpensesAndOtherCurrentLiabilities_24662f6f-e2d4-11e3-5ec9-d3760d571408" xlink:to="loc_us-gaap_AccruedMarketingCostsCurrent_073466e9-e2be-e4b0-bf7c-3c1e90be2873" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OtherAccruedLiabilitiesCurrent" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesCurrent_3b18b100-5c23-de0c-2b69-6ea7677a5a64" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_flks_AccruedExpensesAndOtherCurrentLiabilities_24662f6f-e2d4-11e3-5ec9-d3760d571408" xlink:to="loc_us-gaap_OtherAccruedLiabilitiesCurrent_3b18b100-5c23-de0c-2b69-6ea7677a5a64" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/AccruedExpensesAndOtherCurrentLiabilitiesTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CashEquivalentsAndMarketableSecurities" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CashEquivalentsAndMarketableSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAmortizedCost" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_b671a380-e06c-01fd-905c-c45ee0d0ab53" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_ba478347-bbf1-ddfc-8a79-7775b3b62a6c" xlink:type="locator" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_b671a380-e06c-01fd-905c-c45ee0d0ab53" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_ba478347-bbf1-ddfc-8a79-7775b3b62a6c" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_65f23050-696a-07fd-30c1-78a5110d800c" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_b671a380-e06c-01fd-905c-c45ee0d0ab53" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_65f23050-696a-07fd-30c1-78a5110d800c" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecurities_01be169b-08cc-7c30-55f5-941791d17ef8" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_b671a380-e06c-01fd-905c-c45ee0d0ab53" xlink:to="loc_us-gaap_AvailableForSaleSecurities_01be169b-08cc-7c30-55f5-941791d17ef8" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CashEquivalentsAndMarketableSecuritiesTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CommitmentsAndContingenciesMinimumFutureLeasePaymentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_ab95e8f2-93e0-6140-6e56-a79823c16c0d" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_00eaf688-6963-ad8a-03b8-e257d107b9c7" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_ab95e8f2-93e0-6140-6e56-a79823c16c0d" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_00eaf688-6963-ad8a-03b8-e257d107b9c7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_5519a64c-2a56-b1d5-2ab3-ee16d7d2a7a5" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_ab95e8f2-93e0-6140-6e56-a79823c16c0d" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_5519a64c-2a56-b1d5-2ab3-ee16d7d2a7a5" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CommitmentsAndContingenciesNarrativeDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CommitmentsAndContingenciesTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CommonStock" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CommonStockNarrativeDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CommonStockRestrictedCommonStockActivityDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CommonStockSharesReservedForFutureIssuanceDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/CommonStockTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/ConsolidatedBalanceSheetParenthetical" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_04e17fb3-9b77-1c98-f460-7f5dd0c01008" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_2644da13-7baa-0a2f-63e0-0906a691ba01" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_04e17fb3-9b77-1c98-f460-7f5dd0c01008" xlink:to="loc_us-gaap_StockholdersEquity_2644da13-7baa-0a2f-63e0-0906a691ba01" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PreferredStockValue" xlink:label="loc_us-gaap_PreferredStockValue_3c8f3df4-466c-f78c-b021-17337fc4a147" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_2644da13-7baa-0a2f-63e0-0906a691ba01" xlink:to="loc_us-gaap_PreferredStockValue_3c8f3df4-466c-f78c-b021-17337fc4a147" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockValue" xlink:label="loc_us-gaap_CommonStockValue_d53388e7-4c8c-4e6d-6e90-7a6e0a100b74" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_2644da13-7baa-0a2f-63e0-0906a691ba01" xlink:to="loc_us-gaap_CommonStockValue_d53388e7-4c8c-4e6d-6e90-7a6e0a100b74" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AdditionalPaidInCapital" xlink:label="loc_us-gaap_AdditionalPaidInCapital_27e98f68-fe6c-3420-5b5a-861a4dc60800" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_2644da13-7baa-0a2f-63e0-0906a691ba01" xlink:to="loc_us-gaap_AdditionalPaidInCapital_27e98f68-fe6c-3420-5b5a-861a4dc60800" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_aeb1020a-508a-a8c1-f34c-bafff16c26cb" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_2644da13-7baa-0a2f-63e0-0906a691ba01" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_aeb1020a-508a-a8c1-f34c-bafff16c26cb" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_f759e73e-9f4f-941e-1138-49bc44f6b118" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_2644da13-7baa-0a2f-63e0-0906a691ba01" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_f759e73e-9f4f-941e-1138-49bc44f6b118" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_Liabilities" xlink:label="loc_us-gaap_Liabilities_6d3ec995-5062-ef92-dd72-b570c1eafdc8" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_04e17fb3-9b77-1c98-f460-7f5dd0c01008" xlink:to="loc_us-gaap_Liabilities_6d3ec995-5062-ef92-dd72-b570c1eafdc8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaap_LiabilitiesCurrent_a859bb84-8118-88ec-5136-83fdb14e8f32" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_6d3ec995-5062-ef92-dd72-b570c1eafdc8" xlink:to="loc_us-gaap_LiabilitiesCurrent_a859bb84-8118-88ec-5136-83fdb14e8f32" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="loc_us-gaap_AccountsPayableCurrent_222239a2-3ddd-5e4f-4ae1-b11c60b29d92" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_a859bb84-8118-88ec-5136-83fdb14e8f32" xlink:to="loc_us-gaap_AccountsPayableCurrent_222239a2-3ddd-5e4f-4ae1-b11c60b29d92" xlink:type="arc" />
    <link:loc xlink:href="flks-20161231.xsd#flks_AccruedExpensesAndOtherCurrentLiabilities" xlink:label="loc_flks_AccruedExpensesAndOtherCurrentLiabilities_24662f6f-e2d4-11e3-5ec9-d3760d571408" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_a859bb84-8118-88ec-5136-83fdb14e8f32" xlink:to="loc_flks_AccruedExpensesAndOtherCurrentLiabilities_24662f6f-e2d4-11e3-5ec9-d3760d571408" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredRentCreditCurrent" xlink:label="loc_us-gaap_DeferredRentCreditCurrent_07500f72-f3a0-2e98-9c08-4dd5ebb90c59" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_a859bb84-8118-88ec-5136-83fdb14e8f32" xlink:to="loc_us-gaap_DeferredRentCreditCurrent_07500f72-f3a0-2e98-9c08-4dd5ebb90c59" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredRevenueCurrent" xlink:label="loc_us-gaap_DeferredRevenueCurrent_2e84b53d-95cb-56a2-a5b5-1d31836c02d9" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_a859bb84-8118-88ec-5136-83fdb14e8f32" xlink:to="loc_us-gaap_DeferredRevenueCurrent_2e84b53d-95cb-56a2-a5b5-1d31836c02d9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredRentCreditNoncurrent" xlink:label="loc_us-gaap_DeferredRentCreditNoncurrent_08ba552f-4739-6196-2a2f-236b77ed03f1" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_6d3ec995-5062-ef92-dd72-b570c1eafdc8" xlink:to="loc_us-gaap_DeferredRentCreditNoncurrent_08ba552f-4739-6196-2a2f-236b77ed03f1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_b65887e3-1865-ef3e-c8ae-81780cbff9ee" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_6d3ec995-5062-ef92-dd72-b570c1eafdc8" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_b65887e3-1865-ef3e-c8ae-81780cbff9ee" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaap_Assets_08bee809-e27e-48c3-da2d-5d52948eb470" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaap_AssetsCurrent_dbbeeff9-fd43-6151-195d-0532728ac216" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_08bee809-e27e-48c3-da2d-5d52948eb470" xlink:to="loc_us-gaap_AssetsCurrent_dbbeeff9-fd43-6151-195d-0532728ac216" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_Cash" xlink:label="loc_us-gaap_Cash_31b089b6-cab9-7e98-65c7-eea8ed3f6029" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_dbbeeff9-fd43-6151-195d-0532728ac216" xlink:to="loc_us-gaap_Cash_31b089b6-cab9-7e98-65c7-eea8ed3f6029" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MarketableSecuritiesCurrent" xlink:label="loc_us-gaap_MarketableSecuritiesCurrent_30bbf828-dd37-f00d-1301-5ee8c8abf059" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_dbbeeff9-fd43-6151-195d-0532728ac216" xlink:to="loc_us-gaap_MarketableSecuritiesCurrent_30bbf828-dd37-f00d-1301-5ee8c8abf059" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_d28874fa-4543-5746-c91a-559d7ab47f77" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_dbbeeff9-fd43-6151-195d-0532728ac216" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_d28874fa-4543-5746-c91a-559d7ab47f77" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InventoryNet" xlink:label="loc_us-gaap_InventoryNet_a5201305-cb63-d1e5-f4e7-e25409fb5d3a" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_dbbeeff9-fd43-6151-195d-0532728ac216" xlink:to="loc_us-gaap_InventoryNet_a5201305-cb63-d1e5-f4e7-e25409fb5d3a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_8cc01d89-cd24-22b5-77d4-23f6bae81aca" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_dbbeeff9-fd43-6151-195d-0532728ac216" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_8cc01d89-cd24-22b5-77d4-23f6bae81aca" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_68e7c3c1-9b8d-84fe-3a5c-d69c15dfe7a2" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_08bee809-e27e-48c3-da2d-5d52948eb470" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_68e7c3c1-9b8d-84fe-3a5c-d69c15dfe7a2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_e6ade192-0839-bdd8-d08b-20387a0e8201" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_08bee809-e27e-48c3-da2d-5d52948eb470" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_e6ade192-0839-bdd8-d08b-20387a0e8201" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsNoncurrent" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_3f9aa892-872a-217e-f4da-55b8bc195d22" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_08bee809-e27e-48c3-da2d-5d52948eb470" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_3f9aa892-872a-217e-f4da-55b8bc195d22" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MarketableSecuritiesNoncurrent" xlink:label="loc_us-gaap_MarketableSecuritiesNoncurrent_e30c8c79-60f4-70c9-fee5-2f479316a05e" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_08bee809-e27e-48c3-da2d-5d52948eb470" xlink:to="loc_us-gaap_MarketableSecuritiesNoncurrent_e30c8c79-60f4-70c9-fee5-2f479316a05e" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/ConsolidatedStatementOfCashFlows" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CashPeriodIncreaseDecrease" xlink:label="loc_us-gaap_CashPeriodIncreaseDecrease_7f6792ed-0404-1240-2f7f-c728a0ba443a" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashPeriodIncreaseDecrease_7f6792ed-0404-1240-2f7f-c728a0ba443a" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_8baf87d5-5f2f-7d0d-cb85-b9f249bae0c5" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_NetIncomeLoss_8baf87d5-5f2f-7d0d-cb85-b9f249bae0c5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_Depreciation" xlink:label="loc_us-gaap_Depreciation_b6c36e3f-ea84-a440-1267-34444a0f8e78" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_Depreciation_b6c36e3f-ea84-a440-1267-34444a0f8e78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="loc_us-gaap_ShareBasedCompensation_432488d8-28ca-5b8d-679b-29be120957b5" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_ShareBasedCompensation_432488d8-28ca-5b8d-679b-29be120957b5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OtherNoncashExpense" xlink:label="loc_us-gaap_OtherNoncashExpense_ed1c7de3-044d-73c6-628a-8f76a69dc0b3" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_OtherNoncashExpense_ed1c7de3-044d-73c6-628a-8f76a69dc0b3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInRestrictedCashForOperatingActivities" xlink:label="loc_us-gaap_IncreaseDecreaseInRestrictedCashForOperatingActivities_3e8c8f10-7562-dec5-5d65-c1294986b8e5" xlink:type="locator" />
    <link:calculationArc order="5" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_IncreaseDecreaseInRestrictedCashForOperatingActivities_3e8c8f10-7562-dec5-5d65-c1294986b8e5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_e99fae14-a0f3-93f9-f0e6-bc9b4dc580ef" xlink:type="locator" />
    <link:calculationArc order="6" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_e99fae14-a0f3-93f9-f0e6-bc9b4dc580ef" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentAssets" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_7c8a7ed5-e324-f4d1-e0f2-1bef47015198" xlink:type="locator" />
    <link:calculationArc order="7" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_7c8a7ed5-e324-f4d1-e0f2-1bef47015198" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_503015f3-ea26-0d7a-c655-6d6aff0c5fab" xlink:type="locator" />
    <link:calculationArc order="8" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_503015f3-ea26-0d7a-c655-6d6aff0c5fab" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_ce728eee-c863-e8aa-a864-1d7a3b12d862" xlink:type="locator" />
    <link:calculationArc order="9" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_ce728eee-c863-e8aa-a864-1d7a3b12d862" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredLiabilities_c82499ea-b0f3-4d91-3d78-c1bc0433f8e1" xlink:type="locator" />
    <link:calculationArc order="10" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredLiabilities_c82499ea-b0f3-4d91-3d78-c1bc0433f8e1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_ea2f1c63-e49d-6ee4-286c-9c83476dc9f1" xlink:type="locator" />
    <link:calculationArc order="11" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_ea2f1c63-e49d-6ee4-286c-9c83476dc9f1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentIncomeAmortizationOfPremium" xlink:label="loc_us-gaap_InvestmentIncomeAmortizationOfPremium_4e10c09e-2951-d36f-8a7e-9b8ddbef4387" xlink:type="locator" />
    <link:calculationArc order="12" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_InvestmentIncomeAmortizationOfPremium_4e10c09e-2951-d36f-8a7e-9b8ddbef4387" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_ffe19198-61f8-be6a-6111-42f645804604" xlink:type="locator" />
    <link:calculationArc order="13" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_ffe19198-61f8-be6a-6111-42f645804604" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInInventories" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_bae7c33e-3fd3-413e-0f2e-aaa9daaa49d7" xlink:type="locator" />
    <link:calculationArc order="14" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_bae7c33e-3fd3-413e-0f2e-aaa9daaa49d7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredRevenue" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_38bb77ff-9a71-da5a-ae9a-8c89f84c6b01" xlink:type="locator" />
    <link:calculationArc order="15" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_975a3fab-7f49-5162-2cb5-31bb1479931f" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_38bb77ff-9a71-da5a-ae9a-8c89f84c6b01" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_95f67350-d3ec-5d41-e3b2-a4fe7a19e15b" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashPeriodIncreaseDecrease_7f6792ed-0404-1240-2f7f-c728a0ba443a" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_95f67350-d3ec-5d41-e3b2-a4fe7a19e15b" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PaymentsToAcquireMarketableSecurities" xlink:label="loc_us-gaap_PaymentsToAcquireMarketableSecurities_9cd29e2f-0081-8adc-bf22-3dace6b78eac" xlink:type="locator" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_95f67350-d3ec-5d41-e3b2-a4fe7a19e15b" xlink:to="loc_us-gaap_PaymentsToAcquireMarketableSecurities_9cd29e2f-0081-8adc-bf22-3dace6b78eac" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_837f4053-a450-75ac-2441-cc071e31e63c" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_95f67350-d3ec-5d41-e3b2-a4fe7a19e15b" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_837f4053-a450-75ac-2441-cc071e31e63c" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_991d89e2-25f7-1061-f5f8-86acc91f176b" xlink:type="locator" />
    <link:calculationArc order="3" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_95f67350-d3ec-5d41-e3b2-a4fe7a19e15b" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_991d89e2-25f7-1061-f5f8-86acc91f176b" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_da5d3613-0426-0efc-e877-f02868c1f6ef" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_95f67350-d3ec-5d41-e3b2-a4fe7a19e15b" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_da5d3613-0426-0efc-e877-f02868c1f6ef" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_08614f0c-c3a2-4c92-7c1d-aed5de18fe70" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashPeriodIncreaseDecrease_7f6792ed-0404-1240-2f7f-c728a0ba443a" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_08614f0c-c3a2-4c92-7c1d-aed5de18fe70" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/ConsolidatedStatementOfConvertiblePreferredStockAndStockholdersEquityDeficit" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/ConsolidatedStatementOfConvertiblePreferredStockAndStockholdersEquityDeficitParenthetical" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/ConsolidatedStatementOfOperations" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_11a7c554-b3e3-7a3c-a81e-5c5ff89c25e9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_8baf87d5-5f2f-7d0d-cb85-b9f249bae0c5" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_11a7c554-b3e3-7a3c-a81e-5c5ff89c25e9" xlink:to="loc_us-gaap_NetIncomeLoss_8baf87d5-5f2f-7d0d-cb85-b9f249bae0c5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_800dbb3e-0416-e0ab-a30e-cfaeb17b8c4c" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_8baf87d5-5f2f-7d0d-cb85-b9f249bae0c5" xlink:to="loc_us-gaap_OperatingIncomeLoss_800dbb3e-0416-e0ab-a30e-cfaeb17b8c4c" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InterestIncomeOperating" xlink:label="loc_us-gaap_InterestIncomeOperating_c240bf4d-2aea-7ef8-43dd-5b0aecfd278e" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_8baf87d5-5f2f-7d0d-cb85-b9f249bae0c5" xlink:to="loc_us-gaap_InterestIncomeOperating_c240bf4d-2aea-7ef8-43dd-5b0aecfd278e" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SalesRevenueNet" xlink:label="loc_us-gaap_SalesRevenueNet_f7eb5dbc-6802-ae51-de6b-9a44f4241080" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SalesRevenueGoodsNet" xlink:label="loc_us-gaap_SalesRevenueGoodsNet_dec93aa4-b03e-3954-a272-eeb250ead290" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_SalesRevenueNet_f7eb5dbc-6802-ae51-de6b-9a44f4241080" xlink:to="loc_us-gaap_SalesRevenueGoodsNet_dec93aa4-b03e-3954-a272-eeb250ead290" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OtherSalesRevenueNet" xlink:label="loc_us-gaap_OtherSalesRevenueNet_888a521b-fa37-b5b1-8e28-b2ce12b7ced6" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_SalesRevenueNet_f7eb5dbc-6802-ae51-de6b-9a44f4241080" xlink:to="loc_us-gaap_OtherSalesRevenueNet_888a521b-fa37-b5b1-8e28-b2ce12b7ced6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingExpenses" xlink:label="loc_us-gaap_OperatingExpenses_8018a1c5-8b31-881d-1f35-ba7ca791bffa" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_61ca427c-a8f7-736f-ff6b-927d826fc7fa" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_8018a1c5-8b31-881d-1f35-ba7ca791bffa" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_61ca427c-a8f7-736f-ff6b-927d826fc7fa" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_GeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_2b63fac5-7a72-3880-3fd2-630099895af7" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_8018a1c5-8b31-881d-1f35-ba7ca791bffa" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_2b63fac5-7a72-3880-3fd2-630099895af7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CostOfGoodsSold" xlink:label="loc_us-gaap_CostOfGoodsSold_758fda00-4ec6-2a1a-3601-b22661c1a7ff" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_8018a1c5-8b31-881d-1f35-ba7ca791bffa" xlink:to="loc_us-gaap_CostOfGoodsSold_758fda00-4ec6-2a1a-3601-b22661c1a7ff" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/ConsolidatedStatementsOfComprehensiveLoss" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_663a641c-b103-1e10-d3ec-c078ec7a031b" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_8baf87d5-5f2f-7d0d-cb85-b9f249bae0c5" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_663a641c-b103-1e10-d3ec-c078ec7a031b" xlink:to="loc_us-gaap_NetIncomeLoss_8baf87d5-5f2f-7d0d-cb85-b9f249bae0c5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent" xlink:label="loc_us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent_6bae9137-af31-193c-3d25-ae5a6b05d643" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_663a641c-b103-1e10-d3ec-c078ec7a031b" xlink:to="loc_us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent_6bae9137-af31-193c-3d25-ae5a6b05d643" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/ConvertiblePreferredStock" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/ConvertiblePreferredStockNarrativeDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/DocumentAndEntityInformation" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/FairValueMeasurements" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/FairValueMeasurementsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AssetsFairValueDisclosure" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_1503e99b-7965-ca9e-26eb-ff9af4108a7c" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_5987d7dd-ab82-bea6-ec65-c10216a0873a" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_1503e99b-7965-ca9e-26eb-ff9af4108a7c" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_5987d7dd-ab82-bea6-ec65-c10216a0873a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecurities_01be169b-08cc-7c30-55f5-941791d17ef8" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsFairValueDisclosure_1503e99b-7965-ca9e-26eb-ff9af4108a7c" xlink:to="loc_us-gaap_AvailableForSaleSecurities_01be169b-08cc-7c30-55f5-941791d17ef8" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/FairValueMeasurementsTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/IncomeTaxes" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/IncomeTaxesNarrativeDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/IncomeTaxesScheduleOfDeferredTaxAssetsAndLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:label="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_01ec1572-4ef3-c4fc-b254-d545dc66e953" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxAssetsNet" xlink:label="loc_us-gaap_DeferredTaxAssetsNet_dad43eb1-2d05-8e6b-1503-6a61e00404ca" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_01ec1572-4ef3-c4fc-b254-d545dc66e953" xlink:to="loc_us-gaap_DeferredTaxAssetsNet_dad43eb1-2d05-8e6b-1503-6a61e00404ca" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxAssetsGross" xlink:label="loc_us-gaap_DeferredTaxAssetsGross_344334d8-d156-37ea-1859-beb8bda06f5f" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_dad43eb1-2d05-8e6b-1503-6a61e00404ca" xlink:to="loc_us-gaap_DeferredTaxAssetsGross_344334d8-d156-37ea-1859-beb8bda06f5f" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwards" xlink:label="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwards_6826a434-0eba-a280-99df-92eaa6c3f055" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsGross_344334d8-d156-37ea-1859-beb8bda06f5f" xlink:to="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwards_6826a434-0eba-a280-99df-92eaa6c3f055" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccruals" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccruals_d1418f35-fbc0-ea7c-3165-21e9183ae6c6" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsGross_344334d8-d156-37ea-1859-beb8bda06f5f" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccruals_d1418f35-fbc0-ea7c-3165-21e9183ae6c6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxAssetsPropertyPlantAndEquipment" xlink:label="loc_us-gaap_DeferredTaxAssetsPropertyPlantAndEquipment_34e913c0-b1c2-e857-5bab-9c4547c373b9" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsGross_344334d8-d156-37ea-1859-beb8bda06f5f" xlink:to="loc_us-gaap_DeferredTaxAssetsPropertyPlantAndEquipment_34e913c0-b1c2-e857-5bab-9c4547c373b9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_87cdbec2-773d-bc5a-3050-f979513ecb7f" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsGross_344334d8-d156-37ea-1859-beb8bda06f5f" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_87cdbec2-773d-bc5a-3050-f979513ecb7f" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxAssetsTaxCreditCarryforwards" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxCreditCarryforwards_f1177a25-1e80-13fd-0827-beddb4de2232" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsGross_344334d8-d156-37ea-1859-beb8bda06f5f" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxCreditCarryforwards_f1177a25-1e80-13fd-0827-beddb4de2232" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxAssetsValuationAllowance" xlink:label="loc_us-gaap_DeferredTaxAssetsValuationAllowance_36eb2c32-e98d-f713-df5d-5d9e7e50b88d" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_dad43eb1-2d05-8e6b-1503-6a61e00404ca" xlink:to="loc_us-gaap_DeferredTaxAssetsValuationAllowance_36eb2c32-e98d-f713-df5d-5d9e7e50b88d" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredIncomeTaxLiabilities" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilities_5e84d681-d720-597c-e306-ca1f497f20e3" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_01ec1572-4ef3-c4fc-b254-d545dc66e953" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilities_5e84d681-d720-597c-e306-ca1f497f20e3" xlink:type="arc" />
    <link:loc xlink:href="flks-20161231.xsd#flks_DeferredTaxLiabilitiesTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" xlink:label="loc_flks_DeferredTaxLiabilitiesTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_860b9fbe-8dc8-affe-69d5-bb54a73c5cdf" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxLiabilities_5e84d681-d720-597c-e306-ca1f497f20e3" xlink:to="loc_flks_DeferredTaxLiabilitiesTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_860b9fbe-8dc8-affe-69d5-bb54a73c5cdf" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment_3622af18-6e9e-b903-3573-9cbd06ebe01a" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxLiabilities_5e84d681-d720-597c-e306-ca1f497f20e3" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment_3622af18-6e9e-b903-3573-9cbd06ebe01a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals_d9d80358-26a4-5e39-cf07-7671997bbc4c" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxLiabilities_5e84d681-d720-597c-e306-ca1f497f20e3" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals_d9d80358-26a4-5e39-cf07-7671997bbc4c" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/IncomeTaxesScheduleOfEffectiveIncomeTaxRateReconciliationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_9d686b75-f9ca-45e9-dcb7-a314128deba9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_8e6be169-09a9-5661-71bb-cb6bce1f56f7" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_9d686b75-f9ca-45e9-dcb7-a314128deba9" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_8e6be169-09a9-5661-71bb-cb6bce1f56f7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_a476c969-d3fd-cf02-0d56-ac5fad2f8a34" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_9d686b75-f9ca-45e9-dcb7-a314128deba9" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_a476c969-d3fd-cf02-0d56-ac5fad2f8a34" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_592bc0e7-9233-a559-98bd-046511cfe2a6" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_9d686b75-f9ca-45e9-dcb7-a314128deba9" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_592bc0e7-9233-a559-98bd-046511cfe2a6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost_46b1c974-ca9f-5c7b-d02c-c35ed308faa6" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_9d686b75-f9ca-45e9-dcb7-a314128deba9" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost_46b1c974-ca9f-5c7b-d02c-c35ed308faa6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsResearch" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsResearch_9c9b74e9-df78-b9b1-d558-1a4e6467fc4a" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_9d686b75-f9ca-45e9-dcb7-a314128deba9" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsResearch_9c9b74e9-df78-b9b1-d558-1a4e6467fc4a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationOtherReconcilingItemsPercent" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationOtherReconcilingItemsPercent_b10ff4b5-8f41-b213-a1a9-95afcff1c02c" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_9d686b75-f9ca-45e9-dcb7-a314128deba9" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationOtherReconcilingItemsPercent_b10ff4b5-8f41-b213-a1a9-95afcff1c02c" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance_cf7d450d-2365-800c-0e12-31ac27cc146f" xlink:type="locator" />
    <link:calculationArc order="7" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_9d686b75-f9ca-45e9-dcb7-a314128deba9" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance_cf7d450d-2365-800c-0e12-31ac27cc146f" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/IncomeTaxesTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/Inventory" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/InventoryDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InventoryNet" xlink:label="loc_us-gaap_InventoryNet_a5201305-cb63-d1e5-f4e7-e25409fb5d3a" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InventoryRawMaterialsNetOfReserves" xlink:label="loc_us-gaap_InventoryRawMaterialsNetOfReserves_f925ebd3-061a-e984-2203-e9a7cc583900" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryNet_a5201305-cb63-d1e5-f4e7-e25409fb5d3a" xlink:to="loc_us-gaap_InventoryRawMaterialsNetOfReserves_f925ebd3-061a-e984-2203-e9a7cc583900" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InventoryWorkInProcessNetOfReserves" xlink:label="loc_us-gaap_InventoryWorkInProcessNetOfReserves_7b711a15-f1f0-530a-4653-51844577a7f7" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryNet_a5201305-cb63-d1e5-f4e7-e25409fb5d3a" xlink:to="loc_us-gaap_InventoryWorkInProcessNetOfReserves_7b711a15-f1f0-530a-4653-51844577a7f7" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/InventoryTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/NetLossPerShare" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/NetLossPerShareDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/NetLossPerShareTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/OrganizationAndOperations" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/OrganizationAndOperationsDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/PropertyAndEquipmentNet" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/PropertyAndEquipmentNetDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_68e7c3c1-9b8d-84fe-3a5c-d69c15dfe7a2" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_8c99d26c-e257-b8ba-86ee-4f792a9452ce" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNet_68e7c3c1-9b8d-84fe-3a5c-d69c15dfe7a2" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_8c99d26c-e257-b8ba-86ee-4f792a9452ce" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_95ebcb07-1c4a-1ded-365f-edc9cd2fa101" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNet_68e7c3c1-9b8d-84fe-3a5c-d69c15dfe7a2" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_95ebcb07-1c4a-1ded-365f-edc9cd2fa101" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/PropertyAndEquipmentNetTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/QuarterlyFinancialInformationUnaudited" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/QuarterlyFinancialInformationUnauditedDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/QuarterlyFinancialInformationUnauditedTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/RelatedParties" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/RelatedPartiesDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/RestrictedCash" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/RestrictedCashDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SegmentInformation" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SegmentInformationDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SegmentInformationTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/StockBasedCompensation" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/StockBasedCompensationNarrativeDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/StockBasedCompensationScheduleOfFairValueAssumptionsDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/StockBasedCompensationSummaryOfStockBasedCompensationExpenseDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/StockBasedCompensationSummaryOfStockOptionActivityDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/StockBasedCompensationTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SubsequentEvents" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SubsequentEventsDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPolicies" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPoliciesDepreciationOverEstimatedUsefulLifeDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPoliciesNarrativeDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfChangesInAccumulatedOtherComprehensiveLossDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.flex-pharma.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:type="extended" />
</link:linkbase>