of medical research on the topic over the previous 30 years published in BJU International showed similar results, giving mean flaccid, stretched non-erect, and erect lengths of 9.16 cm, 13.24 cm, and 13.12 cm respectively, and mean flaccid and erect circumferences of 9.31 cm and 11.66 cm respectively. Flaccid penis length can sometimes be a poor predictor of erect length.Ī 2015 systematic review published by Veale et al. As of 2015, a systematic review of 15,521 men, who were measured by health professionals rather than themselves, concluded that the average length of an erect human penis is 13.12 cm (5.17 inches) long, while the average circumference of an erect human penis is 11.66 cm (4.59 inches). Measurements vary, with studies that rely on self-measurement reporting a significantly higher average than those with a health professional measuring.

Compared to other primates, including large examples such as the gorilla, the human penis is thickest, both in absolute terms and relative to the rest of the body. Besides the natural variability of human penises in general, there are factors that lead to minor variations in a particular male, such as the level of arousal, time of day, room temperature, anxiety level, sport activity and frequency of sexual activity.

Human penises vary in size on a number of measures, including length and circumference when flaccid and erect. Diagram showing how to measure the length and circumference of an erect human penis