I'm 5'7, 165-170lbs, athletic build and ordered a L. The arms were perfect length since I have a bit longer arms.It's such a cute, affordable staple piece for your wardrobe. It was a nice thin, it's not too tight or loose; if you like the looser fit, I'd size up from your normal size.I ordered it and it looks as advertised. This is a perfect top for all seasons! I wore it with my blue jean shorts and it looked great. So cute I'll be ordering other tops!