I am 5'9, 175lbs, ordered the large. Had a hard time getting it on, very tight and uncomfortable. The suit is made well, go a size up from what you think you should wear, would work better.
I have used and like the suit, but was very disappointed to receive a pair of large gloves with a medium suit. I'm 5'3" female and these gloves were completely useless to me, I had to order a separate pair on Amazon.