I am 5' 4 1/2", 125 lbs., and ordered a m in this. i'm usually between a s and m. it was too big and didn't have any shape to it. i don't think a s would fit much better. also, i ordered the pink but it was really a coral. if my local store had a s i would probably try it on in a different color, but they don't. i'll have to return this. it looks so cute online.