Ideally the shorts worn by men should be 1 to 3 inches above the knees. Anything longer and you run the risk of entering manpri (Man capri) territory. Wearing anything shorter is a risky proposition; but if you have the confidence and physique to pull it off go for it. For most guys, this is going to be about 5 to 7 inches of inseam if you're about average height. To know the exact length of the inseam, use this formula from GQ for the perfect length shorts.