When I first bought them I used the waist size as my size chart. Being I’ve bought shorts from them before I figured I would be okay. Turned out my quads are bigger than my waist so I reached out to them and they sent me out a bigger size once I returned the original. They were very helpful and quick to respond. Also the shorts are amazing, real light and awesome design. I will say they are a little on the “shorter size” in length so if your looking for shorts that reach your knees, these are probably not them.