How big is the average penis?

When it comes to penis size, there are generally two meaningful dimensions. The first is penis length, the measurement from the base of a man's penis (usually close to where his pubic hair begins) to the tip (where the urethra opens at the end of the glans).

The second dimension is girth, which is the distance around a penis (the circumference), usually measured at the middle of a man's penile shaft. The review of studies in BJU International found that, in a sample of more than 11,500 men, the average penis ranged in length between 5.5 and 6.2 inches and between 4.7 and 5.1 inches in girth. That's in line with the results of a survey by LifeStyle Condoms, which put the average penis size at 5.9 inches long and about 4.9 inches wide.

These measurements refer to the erect penis -- the size of a flaccid penis has little to do with the size of an erection: Some men with small flaccid penises (sometimes jokingly called "growers, not showers") can get much larger when hard; others aren't noticeably bigger.

Scientific studies of the size of erect penises -- and there are a surprising number of them -- consistently show that the average erection is a little more than 5 inches long. Like any aspect of anatomy, though, people vary. On the small side of things, a guy is considered normal if his erect penis is at least 3 inches long. On the long end of things, 2 research efforts found that the longest erect penises in their study populations were about 8 inches long. Longer penises certainly exist, however. In his book Penis Size and Enlargement: Facts, Fallacies, and Proven Methods, Garry Griffin provides the following estimates:

• Only 15% of men have a penis longer than 7 inches when erect.
• Only 3% of men are bigger than 8 inches when erect.
• Only one man in 10,000 has a 10-inch erection.

It's also true that penises that are relatively short when flaccid, tend to enlarge proportionately more during erection than larger penises. In other words, you can't tell from the size of a limp penis how it'll look when erect.

There is tremendous variability regarding the size of the flaccid or non-erect penis. Flaccid penile length is a poor predictor of erectile length. The average erect human penis is approximately 5-6.2 inches (12.7-16 cm). Research studies that rely of self-measurement will report higher than average lengths compared to those measurements made by an investigative staff member. An adult human penis with an erect length of less than 2.8 inches (7cm) but otherwise “normal” in appearance is medically considered to be a micropenis.