How big is a four door car? There are guys at that weight height that are fit and will be much bigger in the chest. There are guys that are belly heavy and will have smaller chests. For the S/M/L stuff some will have narrow shoulders some will be wider. If I went back up to 154 I guess I would be close to a 42 inch. Others might be a 38. A tape measure isn't that expensive. Even a myotape is less then a pair of socks. http://www.amazon.com/AccuFitness-My.../dp/B0017OE4MI True, but i was just after a general guide really. Like when buying suits they usually pair 36inch chest suits with 32 inch trousers and things along that line. I bought a medium sized coat you see and the fitting range is 38-40inch. The small was 36-38 size. Im always confused as to what size to buy. I think i am am about 37 you see and would have prefered to try the small size coat but they had sold out the small which really bug me.