There are many ways to size a leather belt , the easiest way , if you have a belt the person wears and the belt has a heel bar or pin buckle like the one below , measure from the point the pin touches the buckle at the far end ( the left on the illustration below ) to the most used hole in the belt ( usually pretty obvious ). If the belt has a trophy buckle ( big buckle with a small hook on the back that engauges the hole ) measure from that hook to the most used hole.