Bought medium while pregnant (yesss, preggo boobs!) and had to order large. Large fit perfect (I was 150# & 36DD) before wash. Both sizes shrank with wash and the chest bands have expanded with use/wash (Pro & Con, tbh). The clasps still hold like day 1. I wear both the medium and large bc the writing has rubbed off and I can't tell which is which, so either size is okay, but go bigger to allow for swollen mommy titties (&don't forget the titty pads!)