I wear a 7 in juniors and a 4 or 6 in womans depending on the brand. The medium works for me. Haven't had it on in the water yet, and I may regret not getting a small. On the other hand, I wouldn't want it too tight either. I am right in between so it's kinda tough to decide size wise. I do like the sturdiness of the patagonia suits. It doesn't feel like it's going to shift around a lot in the water. Nice thick material.