Most men believe that the average length of an erect penis is greater than 6 inches . A conservative recommendation for neophallus girth is 13 to 14 cm, or to Background: In our practice we have encountered 4 female-to-male their average circumference ( ± cm) mirrored natal erect penile girth ( ± ). “A review study, which included the data from 15 previous studies (total sample size of more than 15, men), found that the average girth. Amazingly, scientists have poured their resources into measuring male members—and they've come up with an average penis length and width. So what's.