If you had to list all of the traits you're looking for in a male partner, it might read something like, "awesome sense of humor, sexy smile, and a shared love of tacos, hiking, and Ozark." Penis size is pretty low on the list of must-have characteristics. 

Still, plenty of men fear their penis size is below average. So what's that defined as? "In the sex-positive world, we like to use a broader spectrum for penis size," says Amy Baldwin, sex educator, sex and relationship coach, and co-host of the Shameless Sex Podcast. "We consider the average penis size in the U.S. to be about four to six inches in length when erect. So a penis of below-average size could be anything less than four inches."