Human penis size

Human penis size refers to the length and width of human male genitalia. Some individuals consider a large penis a sign of masculinity and a small penis a sign of not being able to satisfy a partner's sexual needs. Interest in larger penis sizes have led to an industry devoted to penis enlargement.

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.

Circumference
Penis circumference or girth is measured by using a tape measure or a piece of string and a ruler while the penis is completely erect. It is variously quoted as an average of three measurements: just below the glans penis, in the middle of the shaft, and at the base.

Problems
A penis must be completely erect in order to obtain an accurate measurement. This may be difficult to achieve in a clinical setting. At least one Brazilian doctor resorted to injecting penises with drugs to induce erection, which gave more consistent results. Some clinicians measure the penis by stretching the flaccid penis as far as comfortably possible. Self-reported measurements tend to be unreliable because men often want to report a larger penis size.

Studies on penis size
Self-measurement studies are typically unreliable. Studies have consistently shown that when submitting measurements anonymously in on-line surveys, the average stated penis size is larger than in clinical studies. This is likely due to cultural factors.

Size at birth


The 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.

Size with aging
Age is not believed to negatively correlate with penis size. “Individual research studies have ... suggested that penis size is smaller in studies focusing on older men, but Wylie and Eardley found no overall differences when they collated the results of various studies [over a 60 year period].”

Erect length
Several scientific studies have been performed on the erect length of the adult penis. Studies which have relied on self-measurement, including those from Internet surveys, consistently reported a higher average length than those which used medical or scientific methods to obtain measurements.


 * 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). The purpose of the study was to “provide guidelines of penile length and circumference to assist in counseling patients considering penile augmentation.” Erection was pharmacologically induced in 80 physically normal American men (varying ethnicity, average age 54). It was concluded: “Neither patient age nor size of the flaccid penis accurately predicted erectile length.”


 * 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). Quote: "The aim of this prospective study was to identify clinical and engineering parameters of the flaccid penis for prediction of penile size during erection." Erection was pharmacologically induced in 50 Jewish Caucasian patients who had been evaluated for Erectile dysfunction (average age 47±14y). Patients with penis abnormalities or whose ED could be attributed to more than one psychological origin were omitted from the study.


 * A study conducted by LifeStyles Condoms found an average of 14.9 cm (5.9 in) with a standard deviation of 2.1 cm (0.8 in) (Measured by staff). The purpose of this study was to ensure properly sized condoms were available. 401 college students volunteered to be measured during 2001 Spring Break in Cancún, Mexico, of which 300 gained an erection to be clinically measured (without pharmacological aid). Some of these factors may meet the definition of possible sample bias.

Erect circumference

 * 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).

Similar results exist regarding studies of the circumference of the adult fully erect penis, with the measurement taken mid-shaft. As with length, studies that relied on self-measurement consistently reported a higher average than those with staff measuring.

Flaccid length
One study found the mean flaccid penis length to be 3.5 inches measured by staff). Length of the flaccid penis does not necessarily correspond to length of the erect penis; some smaller flaccid penises can grow much larger, and some larger flaccid penises cannot grow much larger.

The penis and scrotum can contract involuntarily in reaction to cold temperatures or nervousness, referred to by the slang term "shrinkage", due to action by the cremaster muscle.

Penis enlargement surgery
Surgical techniques used for penis enlargement (enhancement phalloplasty) -- penis lengthening and penile widening (girth enhancement) -- have been in the urologic literature for many years.

There two basic ways of enlarging the penis:


 * 1) Penis lengthening surgery involves the release of the fundiform ligament and the suspensory ligament that attaches the 2 erectile bodies to the pubic bone. Once these ligaments have been cut, part of the penile shaft (usually held within the body) drops forward and extends out, enlarging the penis in 2-3 cm.
 * 2) Penis widening with PMMA injection. This method involves injection of silicone, PMMA and other materials into the penis and scrotum, to achieve girth enlargement.

Historical 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. Sources suggest in ancient Greece an uncircumcised and small penis was culturally seen as desirable in a man, whereas a bigger or circumcised penis was viewed as comical or grotesque, usually being found on "fertility gods, half-animal critters such as satyrs, ugly old men, and barbarians."

Modern perceptions
A 2003 study found only 55% of men were satisfied with their penis size, whereas 85% of women were satisfied with their partner’s penis size, and only 6% of women rated their partner as smaller than average. In the same data set, 70% of women expressed dissatisfaction with their breasts, whereas the majority of men (56%) were satisfied with their partner's breasts and only 20% of men wished their partner had larger breasts.

Males may quite easily underestimate the size of their own penis relative to that of others, because of the foreshortening obtained from looking down, or because of the accumulation of fat at the base of the penis. A survey by sexologists showed that many men who believed that their penis was of inadequate size had average-sized penises. Another study found sex education of standard penile measurements to be helpful and relieving for patients concerned about small penis size, most of whom had incorrect beliefs of what is considered medically normal.

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

Popular culture
Culturally, widespread private concerns related to penis size have led to a number of folklore sayings and popular culture reflections related to penis size. These include beliefs that it is possible to predict the size of someone's penis by observing other bodily features such as the hands, feet, nose or height, and in some cases so-called "penis-panic" - a form of mass hysteria involving the believed removal or shrinking of the penis, known as genital retraction syndrome. Penis size, and sexual anxiety generally, have led to products such as penis pumps, pills, and other dubious means of enlargement becoming some of the most marketed products in spam mail.

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. Sex and the City has also shown a character expressing displeasure over her partner having too large a penis, described in comic hyperbolic terms. The media have also been criticized for making "penis envy" into a male body issue equivalent to Cosmopolitan magazine being criticized for their coverage of women's weight.

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

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.

Similar results were found in a cover story published in Psychology Today, which surveyed 1,500 readers (about 2/3 women) about male body image. Many of the women were not particularly concerned with penis size and over 71% thought men overemphasized the importance of penis size and shape. Details were examined among the women with a size preference. Generally women cared more about width than men thought, and less about length. "...the number one reason women preferred a thicker penis was that it was more satisfying during intercourse." It's suggested this is because a wider penis provides more friction to the clitoral area while a longer penis reaches an area less stimulable. The same article comments that there is a strong correlation whereby “women who rated themselves as more attractive were particularly concerned with larger size. Of women describing themselves as much more attractive than average," 64 percent cared strongly or moderately about penis width and 54 percent cared about penis length. Women who rated their own looks as average were about 20 percentage points lower.

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".

The term size queen is slang terminology for a person of either sex who prefers a larger-than-average penis on their sexual partner(s).

Penis size and vaginal response
According to some sex researchers and therapists, several misconceptions have developed surrounding penile-vaginal intercourse. Many men exaggerate the importance of deep vaginal penetration in stimulating a woman to 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, the majority of penises are of sufficient length to satisfy their partners.

Some women find striking the cervix to be uncomfortable or painful, while others report enjoying stimulation of the cervix. The cervix may be confused with the anterior or posterior fornix, the deepest point of the vagina, above and below the cervix, respectively. The cervix and fornix are within close proximity of each other, making it possible for there to 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, also known as the rectouterine pouch, may be indirectly stimulated by pressure on the posterior fornix ).

During arousal, the vagina lengthens rapidly to an average of about 4 in.(8.5 cm), but can continue to lengthen in response to pressure. As the woman becomes fully aroused, the vagina tents (last ²⁄₃ expands in length and width) while the cervix retracts,. The walls of the vagina are composed of soft elastic folds of mucous membrane skin which stretch or contract (with support from pelvic muscles) to the size of the penis. This means (with proper arousal) the vagina stretches/contracts to accommodate virtually any size penis, from small to large.

Micropenis
An adult penis with an erect length of less than 7 cm or just over 2 inches but otherwise formed normally is referred to in a medical context as having the micropenis condition. 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 addressed with growth hormone or testosterone treatment in early childhood.

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
It should be noted that many of the studies conducted on this subject, just as with any other social studies or any scientific studies, have been subject to some sample selection bias and other flaws in the scientific method, especially considering the psychological nature of this specific subject and the ramifications of acquiring accurate data.

Family Health International states "The World Health Organization bases its specifications for condom width on consumer preference and penis size, citing three studies. The studies used varying methods of measurements between sources, such as maximum circumference (US measurements) instead of base circumference (Thai measurements)." The Kinsey reports were based on subjective, self-reported results from African and Caucasian Americans. Taken together, the studies show the most significant variations in penis size are within the population groups themselves, and in general. Two of these self-reported surveys showed that the men of African descent in the study, on average, reported a couple of centimeters more in penis length and width than the Caucasian American men reported. However, the difference between Caucasian and African American penis size found in these subjective tests was insignificant. The study also found that Thai men reported a slightly narrower and shorter size than Caucasian and African Americans while Filipinos (citizens of the Phillipines) were found to have an average penis size that is slightly larger than that of a Caucasian. The Kinsey reports also found that homosexual men reported larger penises than heterosexual men, which underscores the questionablitiy of these studies and self-reported survey methods. The WHO document referred to only specifies whole-population data for the US, Australia and Thailand, and not races in general. Based on the hypothesis that anatomical differences exist among regions, a series of FHI studies were conducted in three Asian countries to compare small and standard width condoms (3.9 cm and 4.9 cm), and in three African countries to compare larger and standard width condoms (5.5 cm and 5.2 cm). According to FHI, "Among the African sites, breakage rates were slightly higher and slippage was slightly lower for the smaller of the two condoms being compared." The data from the Asian sites was inconsistent. FHI concluded that "almost none of the differences in breakage and slippage rates from either the Asian or African sites were statistically significant. Thus, results from these studies pertaining to penis size and condom failure were inconclusive." 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. In 2001 Schneider et al, tested Korean men whose age ranged from 18-19 and 40-68 and measured an erect length of 14.48 cm for the former and 14.18 cm for the latter (14.48±5.7 cm, 14.18±5.58 cm). A report by Dr Kevan Wylie from the Porterbrook Clinic and Royal Hallamshire Hospital found no conclusive differences between the penis size of different races. 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 manufacture." 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 and 30% between 100 and 125 mm [4 to 5 inches] ." The international size standard for condom length is 150 to 180 mm (6 to 7 inches), larger than the average human penis size; thus, the average human penis falls short of international condom size standards. A widespread research done by Dr. Gomez de Diego, director of the medical company Andromedical specialised in andrology, in 2001, took into consideration several studies by physicians of different nationalities. He concluded that the average erect penis size for adult men is 14 cm, confirming the aforementioned research carried out by Dr Eduardo Gomez de Diego. The studies of average erect penis length conducted on adult men worldwide included United States 12.9 cm, France 16 cm, Italy 15 cm, Germany 14.48 cm, Japan 13.0 cm, Saudi Arabia 12.4 cm, Brazil 12.4 cm, India 10.2 cm and South Korea 9.6 cm. 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). To date, there has been no conclusive study linking penis size and race. All studies up to this point have been subject to both self selection bias and sample size flaws.

Penis size and condom use
Various studies have examined condom breakage. Ninety-two monogamous heterosexual couples (aged 18 to 40 for women, 18-50 for men) were enrolled in a prospective study of Durex Ramses condoms. At each sexual encounter, a diary was completed which included information on condom use, and breaks and slips. In France a random telephone survey of 20,000 individuals drew on 4,500 sexually active people, of whom 731 had used a condom in the previous year and 707 provided information on difficulties of use. In Australia 3658 condoms were used by 184 men in a study which looked, inter alia (among other things), at penis size as a factor for breakage or slippage.

Although the most common type of condom, those made of latex, have great ability to stretch, they are vulnerable to dry friction (ie, the dry rubbing motion of sexual activity when there is tight pressure or a lack of smooth lubricated movement) as well as other mistakes of usage. For example, in a separate study of people practicing anal sex, condom breakage was linked more to excessive friction (in this case due to low usage of a sexual lubricant) than to penis size per se.

The rate of condom breakage for correctly used condoms was 1.34% and of slippage 2.05%, with a total failure rate of 3.39%. Penis size did not influence slippage, but penis circumference and broken condoms were strongly correlated, with larger sizes increasing the rate of breakage.