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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-08-07</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001426332</issuerCik>
        <issuerName>NGM BIOPHARMACEUTICALS INC</issuerName>
        <issuerTradingSymbol>NGM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001182464</rptOwnerCik>
            <rptOwnerName>GOEDDEL DAVID V</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1700 OWENS STREET</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 500</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94158</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-08-07</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>224500</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16356743</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                    <footnoteId id="F7"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-08-08</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>12</value>
                    <footnoteId id="F8"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.98</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16356755</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                    <footnoteId id="F7"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-08-09</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>152</value>
                    <footnoteId id="F9"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.99</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16356907</value>
                    <footnoteId id="F10"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                    <footnoteId id="F7"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Consists of  112,250 shares held directly by Ponoi Capital, LP (&quot;Ponoi LP&quot;) and 112,250 shares held directly by Ponoi Capital II, LP (&quot;Ponoi II LP&quot;).</footnote>
        <footnote id="F2">The securities are directly held by Ponoi LP, and indirectly held by Ponoi Management, LLC (&quot;Ponoi LLC&quot;), the general partner of Ponoi LP. The managing partners of Ponoi LLC are David Goeddel, Peter Svennilson and Tim Kutzkey. The managing partners of Ponoi LLC may be deemed to have voting and investment power with respect to such shares. Each individual managing partner disclaims beneficial ownership of these shares, except to the extent of his pecuniary interest in such shares.</footnote>
        <footnote id="F3">The securities are directly held by Ponoi II LP, and indirectly held by Ponoi II Management, LLC (&quot;Ponoi II LLC&quot;), the general partner of Ponoi II LP. The managing partners of Ponoi II LLC are David Goeddel, Peter Svennilson and Tim Kutzkey. The managing partners of Ponoi II LLC may be deemed to have voting and investment power with respect to such shares. Each individual managing partner disclaims beneficial ownership of these shares, except to the extent of his pecuniary interest in such shares.</footnote>
        <footnote id="F4">The securities are directly held by TCG LP, and indirectly held by TCG GP, the general partner of TCG LP. The managing partners of TCG GP are David Goeddel and Peter Svennilson. The managing partners of TCG GP may be deemed to have voting and investment power with respect to such shares. Each individual managing partner disclaims beneficial ownership of these shares, except to the extent of his pecuniary interest in such shares.</footnote>
        <footnote id="F5">The securities are directly held by TCG II LP, and indirectly held by The Column Group II GP, LP (&quot;TCG II GP&quot;), the general partner of TCG II LP. The managing partners of TCG II GP are David Goeddel and Peter Svennilson. The managing partners of TCG II GP may be deemed to have voting and investment power with respect to such shares. Each individual managing partner disclaims beneficial ownership of these shares, except to the extent of his pecuniary interest in such shares.</footnote>
        <footnote id="F6">The securities are directly held by TCG GP. The managing partners of TCG GP are David Goeddel and Peter Svennilson. The managing partners of TCG GP may be deemed to have voting and investment power with respect to such shares. Each individual managing partner disclaims beneficial ownership of these shares, except to the extent of his pecuniary interest in such shares.</footnote>
        <footnote id="F7">The securities are directly held by TCGM LP. The managing partners of TCGM LP are David Goeddel and Peter Svennilson. The managing partners of TCGM LP may be deemed to have voting and investment power with respect to such shares. Each individual managing partner disclaims beneficial ownership of these shares, except to the extent of his pecuniary interest in such shares.</footnote>
        <footnote id="F8">Consists of 6 shares held directly by Ponoi LP and 6 shares held directly by Ponoi II LP.</footnote>
        <footnote id="F9">Consists of 76 shares held directly by Ponoi LP and 76 shares held directly by Ponoi II LP.</footnote>
        <footnote id="F10">Consists of 11,103,333 shares of Common Stock held directly by The Column Group, LP (&quot;TCG LP&quot;), 2,265,758 shares of Common Stock held directly by The Column Group II, LP (&quot;TCG II LP&quot;), 100,000 shares of Common Stock held directly by The Column Group GP, LP (&quot;TCG GP&quot;), 100,000 shares of Common Stock held directly by The Column Group Management, LP (&quot;TCGM LP&quot;), 1,298,908 shares of Common Stock held directly by Ponoi LP, 1,298,908 shares of Common Stock held directly by Ponoi II LP and 190,000 shares held in trust for which David V. Goeddel and Alena Z. Goeddel serve as co-trustees. The Reporting Person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jennifer J. Carlson, Attorney-in-Fact</signatureName>
        <signatureDate>2019-08-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
