Simply measure your waist to determine the appropriate men's jockstrap underwear size for you. Place an elastic measuring tape across your broadest region of the waist. This site will tell you whether your jockstrap size is small, medium, or large. Since a few people sometimes choose to wear a jockstrap with some other pair of underwear that takes your measurements whilst wearing that underwear. The foremost thing you need to be worried about is that you have placed the tape in a proper way and the size you have measured is not too tight and not too loose for you. After you have ensured both these things then the size you have measured it going to be the ideal size for your jockstrap.