Well, as others have stated your best bet is to measure a jacket that fits you well, or even one that doesn’t and take a hard look at what makes it not fit you.I get that arm length, back length, shoulder, P to P and hem etc.
A comment was made a few posts ago about cuff size, sleeve size etc. That is all getting to hard for me. Mostly I am a "tall" version of a L or XL
Measure the sleeve length; too long? Most are in my view, there’s lots of advice online about correct length.
Check a cuff dimension, they tend to be too loose for most guys.
On here some of the best fits I’ve seen are from MrProper. Do a search on him, a lot of his posts have laid out the details of what he specified for the various jackets he’s ordered.