I'm sure this exists in some form or the other, but a quick googling hasn't revealed anything, so I just set out to write it myself.

The Doom 1.9 Shareware Benchmark only prints out the result as "realtics" and "gametics", and for those too lazy to remember how to convert those into FPS, or don't have a calculator by hand, let me offer you a tool that you run after the benchmark, and it will read the values from text mode video memory, do a little multiplication and division on your behalf and present you with the result.

Because, you know, you actually have a beefy computer in front of you - why would you resort to a pocket calculator or your mobile phone for manually calculating the FPS on your retro rig?

This comes in two flavors, one very straightforward libc-using EXE (~ 32 KiB) and one "slightly smaller binary, slightly more involved source file with inline ASM, because we're avoiding some big libc routines" COM (~ 2 KiB).

Source code included.