As mentioned by others, I would size up. I usually wear a medium in Castelli and I got a large, which fits fine. The problem was that I got the gray shorts, which look great until you sweat and then they look terrible. I recommend a darker color.

When Castelli came out with the new Free Aero short I was uncertain if I would like them. I have worn the previous version and really liked them. I was pleasantly surprised by the new design features. The pad is improved (it was always great compared to many brands) and the elastic leg grip design is much improved over the previous. The shorts are very comfortable and do not move around. They do fit small - so order one size up.

This size chart is a joke. These shorts are not made for cyclists with quad muscles. Measure yourself, then order 2 sizes bigger or you won’t be able to put these on. I ordered one size up and still these were a no go. The band at the bottom of the leg is very restrictive.