How long is an average erect penis?

Depends. While results vary across studies, the consensus is that the mean human penis is approximately 12.9–15 CM (5.1–5.9 in) in length with a 95% confidence interval of (10.7 cm, 19.1 cm) (or, equivalently, 4.23 in, 7.53 in). The consensus on typical circumference is 12.3 CM (4.85 in), requiring a diameter of roughly 3.9 CM (1.54 in) when fully erect. Patricio gagollo, pediatric urology dallas, texas.