sha1sum is a utility used to calculate the SHA hash of a file. GnuPG has made a precompiled binary available for Microsoft Windows, while most Unix-like operating systems already include the utility.
Example usage:
bash$ sha1sum "A Dance with Rogues Part 1 V1.30.mod" bbe25cf775bae9578815a9537d34d49487aecbb3 A Dance with Rogues Part 1 V1.30.mod
See also md5sum.