Based on others recommendations I sized up to a Large and I'm glad I did. It fits perfectly. I ordered the White and my main complaint is that it's fairly see through and I'm not comfortable wearing this to work without a cami underneath. While it's not shear, with a skin tone bra, you can see the color of the bra. I'm really disappointed that this is yet another shirt that I have to wear another shirt underneath (especially in really hot weather where the last thing I want to do is wear 2 shirts).  All that said, I like it enough that I plan on order at least one more in a darker color.