For 21 studies in which researchers measured stretched penises, the mean was approximately 5.11 inches (12.98 cm n = 13,719). In this review, the combined mean for 10 studies in which researchers took measurements of erect penises was 5.36 inches (13.61 cm n = 1,629). These studies suffered from both volunteer bias and social desirability bias. This belief is due, in part, to several often-cited studies that relied on self-reported measurements, with means of about 6.2 inches (15.75 cm) for heterosexual men and even greater for gay men.
Most men believe that the average length of an erect penis is greater than 6 inches (15.24 cm).
