I'm between a 4 & 6 depending on the cut and type of clothing. I don't like things tight so I usually get a medium for comfort, which is what I did with the matching bottoms. They were so soft, comfortable & warm that I ordered this matching top after we got home from our ski trip. I'm sure I'll love it too. I wash them in cold water with a detergent that leaves no residue, do not use any type of 'softner', and lay out to dry.