I got this top in a small. It fit perfectly around the trunk of my body and chest. Fit fine around my arms to, even though I lift weights and was slightly concerned that around my arms may be a bit tight. As I have some muscle developed on my triceps. The big issue I have is that I could not raise my arms past around my shoulders while wearing this top. I could have technically forced it, but that would have caused ripping. So forget raising your hand to be called upon in a class, or any other number of daily tasks you may need to do like reaching out for something up high. I am not a big woman with a large back or anything by any means either. I'm maybe 5'4"-5'5" and 125 lbs. I've considered sizing up, but I have a smaller chest and think a medium will be looser around my breasts than I would like. So this shirt is just not for me.