I am 131 lbs, 52, muscular, 34 C and a mother of 1 so I ordered this for future breastfeeding babies but also because I hate wearing full on shirts under my strappy dresses or tank tops because I have to have my shoulders covered for religious reasons. I ORDERED A LARGE! Fits perfectly while I typically wear a medium in tops. MY ONE COMPLAINT about this shirt is that the sleeves don't relax and lay flat. Mine poke outwards so any undershirt worn underneath it is seen because sleeves go straight out over my shoulders, not downwards with the shape of the shoulder. You can see this in my picture