LIMITED POWER OF ATTORNEY

        The undersigned hereby constitutes and appoints each of Sanjiv K. Patel,
Brian R. Adams, Thomas Catinazzo and William D. Collins, signing singly, and
with full power of substitution, the undersigned's true and lawful attorney-in-
fact to:

              (1)   execute for and on behalf of the undersigned, in the
undersigned's capacity as officer and/or director of Relay Therapeutics, Inc.
(the "Company"), from time to time the following U.S. Securities and Exchange
Commission ("SEC") forms: (i) Form ID, including any attached documents (such as
Update Passphrase Authentication), to effect the assignment of codes to the
undersigned to be used in the transmission of information to the SEC using the
EDGAR System; (ii) Form 3, Initial Statement of Beneficial Ownership of
Securities, including any attached documents; (iii) Form 4, Statement of Changes
in Beneficial Ownership of Securities, including any attached documents; (iv)
Form 5, Annual Statement of Beneficial Ownership of Securities in accordance
with Section 16(a) of the Securities Exchange Act of 1934, as amended, and the
rules thereunder, including any attached documents; (v) Schedule 13D and (vi)
amendments of each thereof, in accordance with the Securities Exchange Act of
1934, as amended, and the rules thereunder, including any attached documents;

              (2)   do and perform any and all acts for and on behalf of the
undersigned which may be necessary or desirable to complete and execute any such
Form 3, 4 or 5, Schedule 13D or any amendment(s) thereto, and timely file such
form(s) with the SEC and any securities exchange, national association or
similar authority; and

              (3)   take any other action of any type whatsoever in connection
with the foregoing which, in the opinion of such attorney-in-fact, may be of
benefit to, in the best interest of, or legally required by, the undersigned, it
being understood that the documents executed by such attorney-in-fact on behalf
of the undersigned pursuant to this Power of Attorney shall be in such form and
shall contain such terms and conditions as such attorney-in-fact may approve in
such attorney-in-fact's discretion.

              The undersigned hereby grants to each such attorney-in-fact,
acting singly, full power and authority to do and perform any and every act and
thing whatsoever requisite, necessary or proper to be done in the exercise of
any of the rights and powers herein granted, as fully to all intents and
purposes as the undersigned might or could do if personally present, with full
power of substitution or revocation, hereby ratifying and confirming all that
such attorney-in-fact, or such attorney-in-fact's substitute or substitutes,
shall lawfully do or cause to be done by virtue of this power of attorney and
the rights and powers herein granted.  The undersigned acknowledges that the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, are not assuming, nor is the Company assuming, any of the
undersigned's responsibilities to comply with Section 16 or Regulation 13D-G of
the Securities Exchange Act of 1934, as amended.  The undersigned hereby agrees
to indemnify the attorneys-in-fact and the Company from and against any demand,
damage, loss, cost or expense arising from any false or misleading information
provided by the undersigned to the attorneys-in-fact.

              This Power of Attorney shall remain in full force and effect until
the undersigned is no longer required to file such forms with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to the
foregoing attorneys-in-fact.  This Power of Attorney supersedes any prior power
of attorney in connection with the undersigned's capacity as an officer and/or
director of the Company.  This Power of Attorney shall expire as to any
individual attorney-in-fact if such attorney-in-fact ceases to be an executive
officer of, or legal counsel to, the Company.

              IN WITNESS WHEREOF, the undersigned has caused this Power of
Attorney to be executed as of July 15, 2020.

      /s/ Dipchand Nishar
      ---------------------------
      Name Dipchand Nishar