<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-02-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001447669</issuerCik>
        <issuerName>TWILIO INC</issuerName>
        <issuerTradingSymbol>TWLO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001508900</rptOwnerCik>
            <rptOwnerName>Bessemer Venture Partners VIII L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BESSEMER VENTURE PARTNERS</rptOwnerStreet1>
            <rptOwnerStreet2>1865 PALMER AVENUE, SUITE 104</rptOwnerStreet2>
            <rptOwnerCity>LARCHMONT</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10538</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001508902</rptOwnerCik>
            <rptOwnerName>Bessemer Venture Partners VIII Institutional L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BESSEMER VENTURE PARTNERS</rptOwnerStreet1>
            <rptOwnerStreet2>1865 PALMER AVENUE, SUITE 104</rptOwnerStreet2>
            <rptOwnerCity>LARCHMONT</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10538</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001559306</rptOwnerCik>
            <rptOwnerName>Deer VIII &amp; Co. L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BESSEMER VENTURE PARTNERS</rptOwnerStreet1>
            <rptOwnerStreet2>1865 PALMER AVENUE, SUITE 104</rptOwnerStreet2>
            <rptOwnerCity>LARCHMONT</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10538</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001559311</rptOwnerCik>
            <rptOwnerName>Deer VIII &amp; Co. Ltd.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BESSEMER VENTURE PARTNERS</rptOwnerStreet1>
            <rptOwnerStreet2>1865 PALMER AVENUE, SUITE 104</rptOwnerStreet2>
            <rptOwnerCity>LARCHMONT</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10538</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-02-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3079413</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3079413</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Acquired pursuant to the Agreement and Plan of Merger and Reorganization, dated October 15, 2018, by and between Twilio Inc. (&quot;Twilio&quot;), SendGrid, Inc. (&quot;SendGrid&quot;) and Topaz Merger Subsidiary, Inc., as amended on December 13, 2018 (the &quot;Merger Agreement&quot;, and the transactions contemplated therein, the &quot;Merger&quot;), whereby each share of Common Stock of SendGrid was canceled and automatically converted into 0.485 shares of Class A Common Stock of Twilio, with fractional shares being paid in cash as provided in the Merger Agreement. Bessemer Venture Partners VIII Institutional L.P. (&quot;BVP VIII Inst&quot;) and Bessemer Venture Partners VIII L.P. (&quot;BVP VIII&quot; and, together with BVP VIII Inst, the &quot;BVP VIII Funds&quot;), owned 3,466,721 and 2,882,587 shares, respectively, of SendGrid's Common Stock, which converted in the Merger into 1,681,359 and 1,398,054 shares, respectively, of Twilio's Class A Common Stock.</footnote>
        <footnote id="F2">Deer VIII &amp; Co. Ltd. (&quot;Deer VIII Ltd.&quot;) is the general partner of Deer VIII &amp; Co. L.P. (&quot;Deer VIII L.P.&quot; and, together with Deer VIII Ltd. and the BVP VIII Funds, the &quot;BVP VIII Entities&quot;), which is the general partner of the BVP VIII Funds. Deer VIII Ltd. and Deer VIII L.P. disclaim beneficial ownership of the securities held by the BVP VIII Funds, and this report shall not be deemed an admission that Deer VIII Ltd. and Deer VIII L.P. are the beneficial owners of such securities, except to the extent of their pecuniary interest therein, if any, by virtue of their direct and indirect general partner interests in the BVP VIII Funds.</footnote>
        <footnote id="F3">Byron Deeter is a director of Twilio and is a director of Deer VIII Ltd.  Mr. Deeter also is a director of Deer VII &amp; Co. Ltd. (&quot;Deer VII Ltd.&quot;), which is the general partner of Deer VII &amp; Co. L.P. (&quot;Deer VII L.P.&quot;), which is the general partner of Bessemer Venture Partners VII Institutional L.P. (&quot;BVP VII Inst&quot;), BVP VII Special Opportunity Fund L.P. (&quot;BVP VII SOF&quot;) and Bessemer Venture Partners VII L.P. (&quot;BVP VII&quot;). Each of BVP VII Inst, BVP VII SOF, BVP VII and 15 Angels LLC, a wholly-owned subsidiary of BVP VII Inst (collectively, the &quot;BVP VII Funds&quot; and, together with Deer VII Ltd. and Deer VII L.P., the &quot;BVP VII Entities&quot;), beneficially owns shares of Twilio's Class B Common Stock.  Mr. Deeter serves as a representative of the BVP VII Entities and the BVP VIII Entities on the Board of Directors of Twilio.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Scott Ring, General Counsel, Deer VIII &amp; Co. Ltd., the General Partner of Deer VIII &amp; Co. L.P., the General Partner of Bessemer Venture Partners VIII L.P.</signatureName>
        <signatureDate>2019-02-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Scott Ring, General Counsel, Deer VIII &amp; Co. Ltd</signatureName>
        <signatureDate>2019-02-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Scott Ring, General Counsel, Deer VIII &amp; Co. Ltd., the General Partner of Deer VIII &amp; Co. L.P</signatureName>
        <signatureDate>2019-02-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Scott Ring, General Counsel, Deer VIII &amp; Co. Ltd., the General Partner of Deer VIII &amp; Co. L.P., the General Partner of Bessemer Venture Partners VIII Institutional L.P.</signatureName>
        <signatureDate>2019-02-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
