I wear a medium in most clothes. This medium was a bit too big for me. Overall, I wear a 40R in suit jackets, which provides a snug but well-fitting cut for my semi-athletic build. I am 5'10 with a 170lb frame. Overall, not lean/lanky, but not cut, just bulky while not being overtly fat. Anyways, the shoulders were a bit broader than ideal and the waist left a lot of extra room. Not as snug or well fitting as the picture shows. I felt like I was somewhat "swimming" in the jacket. It was good quality however, and seemed to have a nice weight and feel to the wool. For the price, I would have been satisfied had the cut been good for my frame. However, returned since cut was not good for me.