Definitely size up with this! I couldve gone down maybe one size, but it fits fine in the size I ordered. Its suoer cute and comfy, and the material feels nice. However... if you are outside in this and you sweat, the sweat Really soaks through the material. I touched the shirt and my fingers got super wet from one tiny little bead of sweat. Its a minor complaint but its something I found a little weird, as I was wearing this outside for a while. All in all I am happy with it though!