I fluctuate between a 36DD and 38D and ordered the large. I thought the sports bra fit really well without all my extra fat sticking out (the back near the armpits). Surprisingly, I also thought it provided a good amount of support, more than I thought a medium impact sports bra would. I do use the inserts that come with it. I'm not brave enough yet to use this as a crop top, I put a tank top over it when I workout. If it helps, I do crossfit/HIIT workouts where I always have to run in my workout sessions. I find these to be run approved!
Allie recommended this style