Human penis size

Penis size is of great concern to many people. Some consider having a large penis a mark of masculinity; others are concerned that their penis is too small to satisfy their sexual partner(s). These insecurities have led to many erroneous beliefs about penis size, and to the creation of a whole industry devoted to penis enlargement.

Comparison with other primates

Compared to other primates, even larger primates such as the gorilla, the male human genitalia are remarkably large. The human penis is both longer and thicker than that of any other primate both in absolute terms and in relative size compared to the rest of the body.

Measuring the penis

There are different ways to measure a penis, and some difficulties to overcome while doing so. First of all, a penis must be maximally erect before measurement, and in a clinical setting this is difficult to achieve. At least one Brazilian doctor resorted to injecting penises with drugs to induce an erection, giving much more consistent results. Some clinicians measure the penis by stretching the flaccid penis as far as comfortably possible and take the measurement based on the theory that a fully stretched flaccid penis is equal to an erect penis length. Relying on self-reporting of penis size is problematic, since some patients exaggerate or are unable or unwilling to measure the penis correctly.

Penis length is typically measured with the subject standing and the penis held parallel to the floor. Measurement of length goes horizontally along the top of the penis from the penis's base to the tip. If the penis is measured along the bottom or underside, the result is less reliable. Measurements taken while sitting or lying down also tend to be unreliable.

Girth is measured by using a tape measure. It is variously quoted as an average, at 3 places along the penis, just below the penile head, in the middle of the shaft, and at the base or the thickest part.

Data

There have been several studies regarding the average size of the human penis. The majority of such studies could be unreliable due to self-selection bias: men with a smaller than average penis might be less likely to allow themselves to be measured, while men with a larger than average penis might be more likely to allow themselves to be measured. It is unknown if this conjectured self-selection bias has been confirmed by any studies, or if any studies have attempted to account for potential self-selection bias regarding penis size.

Size at birth

Average stretched penile length at birth is about 4 cm (1.6 in), and 90% of newborn boys will be between 2.4 and 5.5 cm (0.9 and 2.2 in). Limited growth of the penis occurs between birth and 5 years of age, but very little occurs between 5 years and the onset of puberty. The average size at the beginning of puberty is 6 cm (2.4 in) with adult size reached about 5 years later. W.A. Schonfeld published a penis growth curve in 1943.

Erect length

File:Penis frequency.jpg

Frequency graph of LifeStyles data

Percentile plot of LifeStyles data

Regarding the length of the adult fully erect penis (measured along the top of the penis from the groin to the tip), several studies have been performed. Studies that have relied on self-measurement, including those from Internet surveys, consistently reported a higher average than those which used medical or scientific researchers to perform the measurements.

Academic and scientific studies

• A study published in the September 1996 Journal of Urology concluded that average erect length was 12.9 cm (5.08 in)(Measured by staff).

• A study published in the December 2000 International Journal of Impotence Research found that average erect penis length was 13.6 cm (5.35 in)(Measured by staff).

Random sample of college students on spring break

• A study conducted by LifeStyles Condoms during 2001 Spring Break in Cancún, Mexico, found an average of 14.9 cm (5.9 in) with a standard deviation of 2.1 cm (0.8 in)(Measured by staff).

Self measurement surveys

• An Internet survey performed by Sizesurvey.com found an average of 16 cm (6.4 in).

• An Internet survey performed by Jackinworld.com found an average of 15.6 cm (6.1 in).

Erect circumference

File:Penis circum.jpg

Plot of LifeStyles data of circumference

File:Penis circum percentile.jpg

Percentile plot of LifeStyles data of circumference

Similar results exist regarding studies of the circumference of the adult fully erect penis (with the measurement taken mid-shaft). Just as with length, those studies that relied on self-measurement consistently reported a higher average than those that had staff take the measurements, possibly indicating exaggeration when the penis is not scientifically measured.

• A study conducted by LifeStyles Condoms during 2001 Spring Break in Cancún found an average of 12.6 cm (5.0 in) with a standard deviation of 1.3 cm (0.5 in).

Flaccid length

Length of the unencumbered flaccid penis is not necessarily proportional to size of the erect penis. Blood flow from arousal, and its relationship to the subsequent length measurement of the erect penis varies widely among men. Hence a smaller-than-average flaccid penis might grow to five times its flaccid length and twice its girth, or conversely a flaccid penis on the larger side might only grow to 1.5 times the length when filled with blood. The transition to erection and its relationship to measurements is by no means a one-size-fits-all equation.

• A study published in the September 1996 Journal of Urology concluded that mean flaccid length was 8.8 cm (3.5 in)(Measured by staff).

Low temperatures affect the size of the flaccid penis. One general physiological response to cold is decreased circulation of blood to the extremities, which includes the external genitals. The penis will often shrink further as a result.

Perceptions

In a 2005 study by the University of California, Los Angeles, 45% of men responded they would prefer their penis size increased. 84% of respondents rated their penis size as average to above average. (There is a similar perception gap in women's perceptions of their breasts.)

A study undertaken at Utrecht University found that the majority of homosexual men surveyed regard a large penis as ideal, and having one is linked to self esteem.

Men may tend to misjudge the size of their penis relative to that of other men they have seen naked, simply because of the foreshortening effect obtained from always looking down at the penis from above. In addition, as Paul Fussell noted in his memoirs, men who are overweight or have large stomachs may fail to allow for the partial concealment of the penis by their abdomen. The accumulation of fat on the pubic bone above the penis may give a shorter appearance even though the length of the penis from the base is normal.

A survey by sexologists showed that many men who believed that their penis was of inadequate size actually had an average-sized penis. Most sexologists believe that worries about penis size come from some other source of anxiety or perceived inadequacy.

Past perceptions

In ancient Greek art, it is common to see smaller male genitalia than one would expect for the size of the man. Renaissance art also followed this aesthetic; note Michelangelo's David. This was due to the belief that an uncircumcised and small penis was desirable in a man, whereas a bigger or circumcised penis was viewed as comical. This may have had to do with the Greeks' adoration of an undeveloped body or the actual size of real models who stood in cold studios. However, it has also been said that artists intentionally depicted the penis size as smaller than usual, to prevent it from detracting from the art form itself. Others have said that perhaps male average penis size back then was significantly smaller, and has become bigger over time much like the average height has. It is also believed that a large penis was believed to be "beastly" or animal. All of these theories are plausible.

A Priapus figure from Pompeii. Large penises were considered undesirable for men to possess and often depicted for comic effect in ancient Rome.

Urban legends, popular culture, and mass media

In some cultures, mass hysteria involving the believed removal or shrinking of the penis has been observed (genital retraction syndrome).

Many beliefs in popular culture hold that it is possible to predict the size of someone's penis by observing other features. The features usually selected are the hands, the feet, the nose or height. One urban legend suggests that the size of a fully erect penis is the length from the tip of a man's thumb to the tip of his index finger, when a 90° angle is made with these two digits. (An alternative formulation is that this indicates the flaccid penis's length.)

The suggested link between penis size, foot size and height has been investigated by a relatively small number of groups. Two of these studies have suggested a link between penis size and foot size, while the most recent report dismissed these findings. One of the studies suggesting a link relied on the subjects measuring the size of their own penis, which may well be inaccurate. The second study found statistically significant although "weak correlation" between the size of the stretched penis and foot size and height. A potential explanation for these observations is that the development of the penis in an embryo is controlled by some of the same Hox genes (in particular HOXA13 and HOXD13) as those that control the development of the limbs. Mutations of some Hox genes that control the growth of limbs cause malformed genitalia (hand–foot–genital syndrome). However the most recent investigation failed to find any evidence for a link between shoe size and stretched penis size. Given the large number of genes which control the development of the human body shape, and the effects of hormones during childhood and adolescence, it would seem unlikely that an accurate prediction of penis size could be made by measuring a different part of the human body.

Other studies correlating the size of the human penis with other factors have given intriguing results. Notably one study analysing the self-reported Kinsey data set found that homosexual men had statistically larger penises than their heterosexual counterparts. One potential explanation given is a difference in the exposure to androgen hormones in the developing embryo. The study author's opinion is that evidence points towards both orientations being equally likely to exaggerate.

Recently, there has been greater media attention to the issue of penis size and women being more vocal about their preferences. Television shows such as Sex and the City and Ally McBeal popularized the penis-size issue when characters in these TV shows stated their preference for well-endowed men and rejected men who had only average endowment. In HBO's Sex and the City, a female character is portrayed crying in bed when she experiences her boyfriend's penis for the first time and discovers that it is below average length, as opposed to the large length she had expected and anticipated.

The media have been criticized for making "penis envy" into a male body issue equivalent to Cosmopolitan magazine being criticized for their coverage of women's weight. Indeed, one episode of Sex and the City also shows a character expressing displeasure over her partner having too large a penis, though the penis is described in hyperbolic terms and implied to be something of impossibly gargantuan proportions. The British television series Coupling features a running joke on the huge penis of one of the males and the fascination women have with it.

Surveys of women's actual preference have consistently shown that penis size is only a priority for a minority of women, and some women dislike large penises.

In recent years, penis pumps, pills, and other dubious means of penis enlargement have had increased sales. They are one of the most advertised products in spam mail.

Female preference

See also: Size queen

One source of continued debate is the extent to which heterosexual and bisexual women actually prefer certain penis sizes. In a 2005 UCLA study, 85% of women said they were "very satisfied" with their romantic partner's size.

A study published in BMC Women's Health, surveyed women's preferences concerning penis size and concluded that width rather than length is a more important factor of sexual stimulation.

Another study, conducted at Groningen University Hospital, asked 375 sexually active women (who had recently given birth) the importance of penis size and concluded: "Although clearly in the minority, a nevertheless considerable percentage of the women respondents attached substantial importance to the size of the male sexual organ".

Penis size and vaginal response

The vagina itself is a very elastic environment which can expand on average to ~10 centimetres (4 in) in diameter during childbirth, and it also easily retains a tampon. Thus a woman's vagina can tightly accommodate most penises from relatively small to large. It will generally accommodate and adjust to the object it surrounds. Discomfort can sometimes be experienced with unusually large objects, but the vagina can, over time, adapt.

According to Louanne Cole Weston, PhD, licensed counselor, and sex therapist, in a May 2002 report by WebMD, several misconceptions have developed surrounding penile-vaginal intercourse. Cultural preferences may have enlarged the importance of deep vaginal penetration in obtaining female orgasm.

The most sensitive area of the vagina is the section closest to the outside of a woman's body, which is roughly 10 centimeters (4 in) in length. Given that the average penis size is above this length, most men should be able to easily reach and stimulate these erotic nerve endings.

In stark contrast, minor surgery without anesthetic can be conducted on the inner portion of a woman's vagina without discomfort. Most women attest to a feeling of being "filled up" by larger than average penises, yet few can claim to feel erotic sensations in the deeper regions of the vagina. In fact, stimulation of the G-spot may be more effective if the man's penis is slightly shorter than average, as this highly sensitive area of the vagina is located closer to the opening of vagina than to the recesses of its canal (found anywhere from 1 to 3 inches inside the vagina, on the anterior wall).

Some women have reported enjoying stimulation of the cervix, although this may be confused with the anterior fornix (deepest point of vagina above cervix) or posterior fornix (back of vagina, behind cervix). The cervix, fornix, and cul-de-sac are within close proximity of each other, so there may be indirect and/or simultaneous stimulation between them.

The fornix is said to be another possible orgasm trigger area. Tests have shown that pressure on this area causes the vagina to lubricate very quickly. The area of sexual response in the anterior fornix has also been called the epicentre, T-Spot, AFE-Zone, AFE or A-Spot; while in the posterior fornix it has been called epicenter (as well) or cul-de-sac (since the cul-de-sac may be indirectly stimulated by pressure on the posterior fornix).

No matter the size of a man's penis it takes a level of skill to stimulate the anterior fornix. The man with a shorter penis may also be able to stimulate the anterior fornix using some advantageous positions which shorten the distance to the uterus.

Long penises (over ~20 centimeters (8 in)) can be susceptible to rubbing on, or striking, the cervix, which has been described as being rather uncomfortable, or sometimes painful. Over-stretching the back of the vagina can also cause discomfort, and this may be mistaken for cervix pain. Thus very long penises sometimes cannot be fully inserted. The exact depth depends on both anatomical dimensions and arousal of the woman, as well as the sexual technique used.

During sexual intercourse, the vagina lengthens rapidly after initial insertion from about 10 to 14 cm (4 to 5.5 in), but the final and initial depths vary from woman to woman ±2.5 cm (±1 in). The vagina (with proper arousal) will stretch to envelop larger sizes (up to a point) — about 19–23 cm (7.5–9 in) maximum on average (although more may be accommodated with long-term adaptation). As the woman becomes fully aroused the vagina tents (last ²⁄₃ expands in length and width) while the cervix retracts, meaning that with the right penetration angle long penises will slide over or under the cervix without directly hitting it (instead stretching the back of the vagina or anterior/posterior fornix). Enough foreplay to produce full arousal is generally needed to ready a woman for penetration by a large penis — although this same amount of foreplay is often recommended regardless of the man's penis size. While a long penis normally isn't a hindrance, there's little to suggest it's advantageous either.

On the other hand, stimulation of the G-Spot may be more effective if the man's penis is thicker than average, since the pleasure sensations from this area are activated primarily by pressure. A thicker penis may provide more friction against the vestibular bulbs, which are located in close proximity and anteriorly on either side of the urethra. Additionally, some claim that if a penis is thick enough compared with the vaginal opening, i.e. vulva, stretching will occur. This stretching can supposedly cause the clitoral hood to pass back and forth across the clitoris, which would provide additional stimulation of this large concentration of nerve endings. This stretching is claimed to pull the clitoris down into the path of the thrusting penis, causing it to make contact with, and rub across, the top, or dorsal, section of the penis. This may facilitate even greater clitoral stimulation.

Women have confirmed in surveys the primary focus of the clitoris in sexual stimulation. Roughly three-quarters of women surveyed have reported difficulty reaching orgasm by vaginal intercourse alone, and just 7% are able to do this on most occasions. Many report requiring simultaneous clitoral and vaginal stimulation — regardless of the dimensions of the inserted object.

Micropenis

Main article: Micropenis

A penis whose stretched flaccid length is more than approximately 2.5 standard deviations below average size for the age group but otherwise formed normally is referred to in a medical context as a micropenis. Some of the identifiable causes are deficiency of pituitary growth hormone and/or gonadotropins, mild degrees of androgen insensitivity, a variety of genetic syndromes, and variations in certain Homeobox genes. Some types of micropenis can be improved with growth hormone or testosterone treatment in early childhood. Penis-enlargement self-treatments are not effective for this condition

The smallest penis on record was reported in a medical journal by researchers from Oxford University's Department of Physiology, Anatomy and Genetics. The researchers noted that patient "Alfred," a male musician, in his early 30s, from Oxfordshire, UK., "possessed a penis almost indistinguishable from a clitoris." Currently there is much debate in the medical community as to whether patient "Alfred" was actually male or intersexed.

A news post on New Scientist dated December 6, 2004 reads "A new surgical procedure has allowed men with abnormally short penises to enjoy a full sex life and urinate standing up, some for the first time. Tiny "micro-penises" have been enlarged to normal size without losing any erogenous sensation, say UK doctors."

Race and penis size

Differences in average penis size between different races has been a subject of considerable controversy.

The cultural issues involved with the question of race and penis size are complex, with both larger and smaller penises used as justification for regarding other races as inferior; as evidence of an oversexed and brutish animal nature in the former case, or of sexual inadequacy in the latter case. In general, there is a tendency to see the penis size of one's own group as the "right" size, compared to those of others.

There is considerable debate as to whether specific racial variations in penis size exist, and if they do, whether observed variations can be explained in terms of other factors such as correlations of penis size to body size. In any case, within-group variation in penis size (±30%, see above) seems to be considerably larger than claimed between-group variation of average penis size (±4%, see below).

To date, there has been no conclusive evidence that race and penis size are at all correlated and all studies that have been done have been rejected by the scientific community due to inaccuracy, respondent bias, or unverifiable claims.

• A 2002 Survey, "Can shoe size predict penile length?" was conducted to establish if the belief in whether the size of a man's penis can be estimated from his shoe size has any basis in fact. Two urologists measured the stretched penile length of 104 men in a prospective study and related this to their shoe size. The median stretched penile length for the sampled population was 13 cm (5.1 in) and the median UK shoe size was 9 (European 43). There was no statistically significant correlation between shoe size and stretched penile length.

• A 2001 study on penis size among young Italian males in a random group of 3,300 young men ages 17-19 showed "median/large values of penile dimensions recorded in the present study are flaccid length 9.0 cm, flaccid circumference, at the middle of the shaft, 10.0 cm, and stretched length 12.5 cm. We also observed that the penile dimensions are highly correlated with height and weight."

• A test-retest study was done in 2002. The study aimed to establish the test-retest reliability of measurement of the erect penis using paper strips in a sample of 312 gay men. The men were issued with color-coded measuring strips printed with instructions but no calibrations, and asked to measure both the length and circumference of their partners' erect penis. Three months later they were asked to repeat these measures. Mean length on first measurement was 15.3 cm (6.02 in) and 15.2 cm (5.98 in) on second measurement. Mean girth at first measurement was 12.5 cm (4.92 in) and 12.6 cm (4.96 in) at second measurement. Test-retest reliability of measurement was found to be moderately low at r = 0.60 for length and r = 0.53 for girth"

• One of the earliest researchers on the subject, Frantz Fanon, covers this subject in some detail in Black Skin, White Masks (1952), where he tends towards the view that the supposed positive correlation between penis size and African ancestry is erroneous, a conclusion that he also supports with statistics.

• In 2001 Schneider et al, 2001 who tested Korean men whose age ranged from 18-19 and 40-68 measured an erect length from 14.48 cm and for the second group tested, 14.18 cm (14.48±5.7 in, 14.18±5.58 in).

Investigator	Age Range (yr)	Flaccid Length (cm)	Stretched Length (cm)	Erect Length (cm)
Wessels et al, 1996	21–82	8.85	12.45	12.89
Smith et al, 1998	NA	NA	NA	15.71
Schneider et al, 2001	18–19	8.6±1.5	NA	14.48±1.99
	40–68	9.22±1.67	NA	14.18±1.83
Son et al, 2003	19-27	6.9±0.8	9.6±0.8	NA

The BBC reported an Indian Council of Medical Research study finding that "about 60% of Indian men have penises which are between three and five centimetres shorter than international standards used in condom." However, the study also stated that "data collected in Mumbai till 2001 showed that 60% of the participants measured 126 to 156 mm [5 to 6.1 inches] in length." So, according to the study, most Indian men have penises within the average human size range. The international size standard for condom length is 150mm to 180mm (6 to 7 inches). The BBC article's assertion that Indian men's penises are shorter than the international standards for condom manufacture could equally apply to American men according to studies. The report neglected to mention whether the measurements were of erect or flaccid penises.

• In a 2005 study, "Penile measurements in normal adult Jordanians and in patients with erectile dysfunction," the purpose of the work was to determine penile size in adult normal (group one, 271) and impotent (group two, 109) men. In group one mean midshaft circumference was 8.98±1.4 cm (3.54±0.55 in), mean flaccid length was mean 9.3±1.9 cm (3.66±.75 in), and mean stretched length was 13.5±2.3 cm (5.31±.91 in). In group two, mean flaccid length was 7.7±1.3 cm (3.03±.51 in), and mean stretched length was 11.6±1.4 cm (4.57±.55 in).

See also

• Penis envy
• Phalloplasty
• Penis enlargement

References

• The Kinsey Institute penis size bibliography
• Sutherland et al. "The effect of prepubertal androgen exposure on adult penile length." Journal of Urology, Vol. 156(2S), 783-787, 1996.
• Lee PA, et al. "Micropenis. I. Criteria, etiologies, and classification." Johns Hopkins Med J 1980; 146:156.
• W.A. Schonfeld, Am J Dis Child 1943;65:135
• Niels Lauersen, M.D. and Steven Whitney, "It's Your Body: A Woman's Guide to Gynecology", 3rd Edition 1983, p. 480 (Berkley Publishing Co.: New York), ISBN 0-425-09917-2
• Bogaert, A. F., & Hershberger, S. L. (1999). The relation between sexual orientation and penile size. Archives of Sexual Behavior 28:213-221.(PMID:10410197)[1]
• Mortlock DP, Innis JW (1997) Mutation of HOXA13 in hand-foot-genital syndrome.Nat Genet 15(2):179-80.(PMID:9020844)[2]
• Goodman FR (2002) Limb malformations and the human HOX genes. Am J Med Genet 112(3):256-265(PMID:12357469)[3]
• Shah, J. & Christopher, N. (2002) Can Shoe Size Predict Penile Length? BJU Int 90(6):586-7 (PMID:12230622)[4]
• Siminoski K and Bain J (1993) The Relationship Among Height, Penile Length, and Foot Size. Annals of Sex Research 6(3):231-235
• Kondo T, Zakany J, Innis JW, Duboule D.(1997) Of fingers, toes and penises. Nature 390(6655):29(PMID:9363887)[5]
• Rushton, J.P. & Bogaert, A.F. (1987) Race differences in sexual behavior: Testing an evolutionary hypothesis. Journal Research in Personality 21(4): pp. 536-7
• Eisenman, Russell (2001) "Penis size: Survey of female perceptions of sexual satisfaction", PubMed Central (PMC)

External links

• Kinsey Institute An information page on the penis.
• Penis Size Based on Body Parts
• Findings in a Hong Kong Study of Flaccid Penises
• Jackinworld.com Size Survey
• Jackinworld.com Size by Age
• Patient Queries - Penis Size Queries related to penis size answered by Sexologists & Psychiatrists.
• "Give a Man Six Inches and He'll Want a …", The Age Newspaper, Melbourne, Australia, August 13, 2006 article on human penis size and online penis enlargement programs.
• Documentary of Penis Pictures and Surveys Devoted to proving the penis is more than a size.