Im 56, usually btwn 130-135 lbs, size 6 pants, and usually a small-medium top at stores like Express, and a medium in this top was perfect. It is tight medium, but since its a crop top, I didn't want it loose so it would look better with a high-waisted skirt. A size small would have been way too snug & would not even fit. The white is a little transparent, but not too bad. I would definitely buy again.  People are always shocked that I got this from Amazon & how cheap it is! (Skirt pictured is by Morning Lavender)