The average American man’s penis is 5.6 inches (14.2 centimeters) long when erect, a new survey of 1,661 men finds. The study, published online July 10 in the Journal of Sexual Medicine, is relatively consistent with the results of prior surveys of penis size. Penis size has been the subject of dozens of studies, as well as countless urban legends, myths and spam emails. For many men, the idea of not measuring up can cause a great deal of anxiety. But whether penis size truly matters to a man’s sex partner is up for debate.