I'm 5' 1/2'' and weigh 88 pounds with narrow shoulders. Still I ordered MEDIUM. I just fits my shoulders,( no room for me to sew in shoulder pads, which I often do.) Just fits my 33-34" bust.  Forget the hips. My hips are 34" and the material is tight I would have to wear non zippered pull on slacks or jeggings. I tried that and it still doesn't look right. I should have ordered large. But who would if they weigh 88 pounds? The material is nice and light, so if there is a clan of tiny women out there: go for it. This will be a sleep top for me...