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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

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

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001477425</issuerCik>
        <issuerName>SendGrid, Inc.</issuerName>
        <issuerTradingSymbol>SEND</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001506450</rptOwnerCik>
            <rptOwnerName>Deeter Byron B</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>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-02-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>44019</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-02-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6349308</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Disposed of pursuant to the Agreement and Plan of Merger and Reorganization dated as of October 15, 2018, as amended on December 18, 2018 (the &quot;Merger Agreement&quot;, and the transactions contemplated therein, the &quot;Merger&quot;), by and among the Issuer, Twilio Inc. (&quot;Twilio&quot;) and Topaz Merger Subsidiary, Inc., whereby each share of Issuer common stock was canceled in exchange for 0.485 of a share of Twilio Class A Common Stock, with fractional shares being paid in cash.</footnote>
        <footnote id="F2">Includes 5,651 restricted stock units (each, an &quot;RSU&quot;) held by the Reporting Person that at the effective time of the Merger were cancelled and converted into a right to receive 2,740 fully-vested shares of Twilio Class A Common Stock. Also includes 38,368 shares of Issuer common stock previously received by the Reporting Person from the BVP VIII Funds (as defined below) pursuant to one or more pro-rata distributions made in accordance with the exemptions afforded by Rules 16a-13 and 16a-9 of the Securities Exchange Act of 1934, as amended.</footnote>
        <footnote id="F3">The Reporting Person has agreed to assign to Deer Management Co. LLC the right to any shares issuable pursuant to RSU shares or any proceeds from the sale thereof.</footnote>
        <footnote id="F4">Represents 3,466,721 and 2,882,587 shares disposed of by 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;), respectively, pursuant to the Merger Agreement.  At the effective time of the Merger, such shares converted into a right to receive 1,681,359 and 1,398,054 shares of Class A Common Stock of Twilio, respectively.</footnote>
        <footnote id="F5">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;), which is the general partner of the BVP VIII Funds. Mr. Deeter is a director of Deer VIII Ltd. Mr. Deeter disclaims beneficial ownership of the securities held by the BVP VIII Funds, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities, except to the extent of his pecuniary interest, if any, in such securities by virtue of his interest in Deer VIII Ltd, his interest in Deer VIII L.P., and his indirect limited partnership interest in the BVP VIII Funds.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Matthew P. Dubofsky, Attorney-in-Fact</signatureName>
        <signatureDate>2019-02-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
