So I read allot of the reviews on this before I decided on a size. I didn't want it to be too big so I ordered my typical size  S. For reference I'm 5'4" and about 115 w a petite frame. The jacket fits perfectly. I even put on my Under Armour storm hoodie and then the jacket and there was still plenty of extra room to move. Glad I did not order a M bc I think it would have been too big and frumpy. I did not get to try out how it will hold up in a rain storm but I will definitely be putting it to the test in a few days!