I have a 39.5 inch chest measurement, but smaller cup size (B) and an athletic build. I'm always torn about what size to get, but I took a chance on the Medium and it's perfect! Tight enough to provide great support, but not so tight that I'm spilling out. Tasteful cleavage👍🏻
Only reason for 4 stars and not 5 is that the adjustable straps are a little finicky, and don't adjust super smoothly. 5/5 fit, though!