I'm 5'2" and weigh 98 lbs. Chest is 30" round when measured just below my boobs, which are sadly small (A cup). I got this sports bra in size S and it fit me perfectly. It stayed put during my weights training this evening (all my lifts are done on an exercise ball). This bra did not shift even half an inch. I never had to adjust it during my 90-minute workout. The straps did not cut into my shoulders and the band was snug but not uncomfortable. All this for only twelve bucks?! Fantastic!