I picked the medium. The bottom part of the bathing suit fit me perfectly, however, the top could not hold my boobs at all. Not made for those with big boobs. I am 137 lbs, but with with some curves. I wear a 6 in pants and a medium or large t-shirt because I am a 34 DDD. A medium or large bathing suit usually does stretch to fit my chest decently at least because I have a smaller build everywhere else, but these gave me EXTREME side boob and spillage...lol! There is no stretch in it at all. The top is very stiff.  I had to return it. I believe if I got a larger size, the bottom would just get loose and baggy and the top will probably still fit too tight. There is just no stretch in it at all. But it is sooo cute I wanted it to fit so bad.