A 2015 study¹ of the size of the human penis, a meta-analysis based on 17 previous studies, found that
(as many men larger
* A statistical measure. In a case like this, 95% of all men would be expected to fall within ± 2 standard deviations from the mean. The bigger the SD, the more this length varies among men. If the SD for erect penis length were zero, all men would have the same length. Nothing to do with sexual deviants.
The lengths reported were measured along the top, to the tip of the meatus. The foreskin was not included. At the torso end, the end of the tape measure was pressed down to the bone. To see how, view the YouTube video.² The circumferences were measured on the shaft, not over the corona.
Notice that the limp stretched penis is roughly the same length as the erect penis. In a few of the 17 studies analyzed, flaccid stretched lengths were notably shorter than erect lengths. An earlier study3 had found that a limp penis must be stretched with a force of about 4.5 newtons to reach its full potential erect length, and probably some urologists hadn't pulled that hard.
The above figure for the mean length of the erect penis may be a bit too small, as there seems to be some evidence that erections in a clinical setting are shorter than those in the bedroom. Also, the data set for erections was smaller than that for limp penises.
Length is not related to reproductive ability. Fathers have been shorter than 3 cm, and lengths as great as 30 cm are reported. In general, smaller penises lengthen proportionally more than large ones do during an erection, but though the difference between small and large is reduced, the larger remain larger.
Some psychologists believe that the ready availability in recent years of pornography featuring male actors at the far edge of the penile size range has given many men a troubling but distorted conception of what constitutes “normal” penile size. In extreme cases, this anxiety becomes an illness known as Body Dysmorphic Disorder.
As penises go, humans’ are not wonders of the animal world. In many mammals—the raccoon, for example—the penis is stiffened with a bone, something men must pay a surgeon to achieve, and in plastic at that. In size humans are dwarfed: the bull’s is 3 feet, the elephant’s 5 feet, the blue whale’s 7 to 8 feet, and even a small animal like a pig, domestic or wild, has 18 inches. However, humans do have the longest flaccid penis of any primate.
Counselors, marriage handbooks, and sensitive women assure us that there is no correlation between penile size and lovemaking ability. Academic papers espousing the view that women don't care about size have relied on surveys collecting opinions. Xaviera Hollander, an author who claims professional expertise of a practical sort, agrees about the lovemaking but says size does matter, and comments: “Men worry mainly about length, whereas women care more for girth.… If he’s all the way in, up against her cervix, yet there are still two inches on the outside, those are two useless inches. Girth is another matter.… A penis is hardly ever too thick.”4
A 2013 study5 also suggests that size does matter, but to attractiveness rather than in facilitating response to copulation. Australian women were shown projected, life-size, digitally-generated moving images of a full frontal nude man and asked to rate the man's sexual attractiveness on a scale from 1 to 7. The images differed in 3 ways: height, shoulder-to-hip ratio, and penis size (the women were not informed what the variables were). The variable that most was closely associated with attractiveness was height, as previous studies have found. Surprisingly, the shoulder-hip ratio and penis size came in as about equal in affecting attractiveness. The sample size was small (only 105 subjects).
possibly in the species' pre-clothed existence
One of the most curious facts about the human penis is that, of all the organs of the male body, e.g., heart, lungs, brain, liver, and so on, the size of the penis is least related to skeletal size.6
An old myth holds that penis size is correlated to shoe size; the bigger the shoe, the longer the penis. A scientific study has shown that this is not true.1,7
For many years, the ratios between the lengths of fingers has been suspected to be correlated with penile length. The mechanism suggested for such a correlation is the effect of hormones in the womb.
1. David Veale, Sarah Miles, Sally Bramley, Gordon Muir and John Hodsoll.
Am I normal? A systematic review and construction of nomograms for flaccid and erect penis length and circumference in up to 15521 men.
BJU International, first published online 2 March 2015.
BJU International has made this article freely available. Curious readers can download the pdf and use the nomographs to find what percentile they fall into.
2. If pushing down is unclear, it is illustrated in a video from King's College urologists: https://www.youtube.com/watch?v=B045jjH3PZ4
3. J. Chen, A. Gefen, A. Greenstein, H. Matzkin and D. Elqad.
Predicting penile size during erection.
International Journal of Impotence Research, vol 12, pages 328-333 (2000).
4. Xaviera Hollander.
New American Library, 1976.
5. Brian S. Mautz, Bob B. M. Wong, Richard A. Peters, and Michael D. Jennions.
Penis size interacts with body shape and height to influence male attractiveness.
PNAS. Published online before print April 8, 2013.
6. G. A. Piersol.
Philadelphia: Lippincott, 1907.
Confirmed by Masters and Johnson, Human Sexual Response, 1966, page 192.
Robert Latou Dickinson.
Human Sex Anatomy.
Baltimore: Williams and Wilkins, 1933.
P. Bondil, P. Costa, J. P. Daures, J. F. Louis, H. Navratil.
Clinical study of the longitudinal deformation of the flaccid penis and its variations with aging.
European Urology, vol. 21 no. 4, pages 284-286 (1992).
7. Jyoti Shah and N. Christopher.
Can shoe size predict penile length?
BJU International, vol 90, pages 586-587. (2002)
An earlier study had found a weak correlation:
K. Siminoski and J. Bain.
The relationships among height, penile length, and foot size.
Annals of Sex Research, vol. 6, pages 231-235 (1993).
6. digit ratio studies
Mels van Driel.
Paul Vincent, translator.
Manhood. The Rise and Fall of the Penis.
London: Reaktion Books, 2009.
An authoritative entertainment for laymen written by a Dutch urologist.
David M. Friedman.
A Mind of Its Own: A Cultural History of the Penis.
Free Press, 2001.
A compendium on attitudes over the ages.
J. L. McCary.
Sexual Myths and Fallacies.
New York: Van Nostrand Reinhold Co., 1971.
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Last revised: 19 March 2015.