The most accurate measurement of the size of a human penis can be derived from several readings at different times since there is natural minor variability in size depending upon arousal level, time of day, room temperature, frequency of sexual activity, and reliability of measurement. When 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.
Measurements vary, with studies that rely on self-measurement reporting a significantly higher average than those with a health professional measuring. As of 2015, a systematic review of the best research to date on the topic has concluded that the mean length of an erect human penis is approximately 13.12 ± 1.66 cm (5.17 ± 0.65 in). Flaccid penis length is generally a poor predictor of erect length.
Most human penis growth occurs between infancy and the age of five, and between about one year after the onset of puberty and, at latest, approximately 17 years of age.
A statistically significant correlation between penis size and the size of other body parts has not been found in research. Some environmental factors in addition to genetics, such as the presence of endocrine disruptors, can affect penis growth. An adult penis with an erect length of less than 7Â cm (2.8Â in), but otherwise formed normally, is referred to in medicine as a micropenis.
Penis size is positively correlated with increasing testosterone levels during puberty. However, after puberty, administration of testosterone is not capable of affecting penis size, and androgen deficiency in adult men only results in a small decrease in size. Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are also involved in penis size, with deficiency (such as that observed in growth hormone deficiency or Laron syndrome) at critical developmental stages having the potential to result in micropenis.
Studies
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While results vary slightly across reputable studies, the consensus is that the mean human penis, when erect, is in the range 12.9â€"15 cm (5.1â€"5.9 in) in length with a 95% confidence interval of (10.7 cm, 19.1 cm) or, equivalently (4.23 in, 7.53 in) â€" that is, it is 95% certain that the true mean is at least 10.7 cm but not more than 19.1 cm.
A 2015 systematic review published by Veale et al. 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 9.16Â cm, 13.24Â cm, and 13.12Â cm respectively, and mean flaccid and erect circumferences of 9.31Â cm and 11.66Â cm respectively. Erect lengths in the included studies were measured by pushing the pre-pubic fat pad to the bone, and flaccid or erect girth (circumference) was measured at the base or mid-shaft of the penis.
Length
Flaccid
One study found the mean flaccid penis length to be 3.5 inches (8.9 cm) (measured by staff). A review of several studies found average flaccid length to be 9â€"10 cm (3.5â€"3.9 in). Length of the flaccid penis does not necessarily correspond to length of the erect penis; some smaller flaccid penises grow much longer, while some larger flaccid penises grow comparatively less.
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. The same phenomenon affects cyclist and exercise bike users, with prolonged pressure on the perineum from the bicycle saddle and the straining of the exercise causing the penis and scrotum to contract involuntarily. An incorrect saddle may ultimately cause erectile dysfunction (see crotch pressure for more information).
Stretched
Neither age nor size of the flaccid penis accurately predicted erectile length. Stretched length has correlated with erect length in some cases. However studies have also shown drastic differences between stretched and erect length.
Erect
Scientific studies have been performed on the erect length of the adult penis. Studies that have relied on self-measurement, including those from Internet surveys, consistently reported a higher average length than those that used medical or scientific methods to obtain measurements.
The following staff-measured studies are composed of different subgroups of the human population (i.e., specific age range or race; selection of those with sexual medical concerns or self-selection) that could cause a sample bias.
- In a study of 80 healthy males published in the September 1996 Journal of Urology an average erect penis length of 12.9Â cm (5.1Â in) was measured. 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 in 50 Jewish Caucasian males was 13.6 cm (5.4 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 review published in the 2007 issue of BJU International showed the average erect penis length to be 14â€"16 cm (5.5â€"6.3 in) and girth to be 12â€"13 cm (4.7â€"5.1 in). The paper compared results of twelve studies conducted on different populations in several countries. Various methods of measurements were included in the review.
- An Italian study of about 3,300 men published in European Urology concluded that flaccid stretched length was measured on average to about 12.5 centimetres (4.9 in). In addition, they checked for correlations in a random subset of the sample consisting of 325 men. They found a few statistically significant Spearman's correlations: between flaccid length and height of 0.208, âˆ'0.140 with weight, and âˆ'0.238 with BMI, flaccid circumference and height 0.156, stretched length and height 0.221, weight âˆ'0.136, BMI âˆ'0.169. They also reported a few non-significant correlations.
- An Indian study of 500 men ages 18 to 60 published in the International Journal of Impotence Research found flaccid, stretched and erect length to be 8.21Â cm, 10.88Â cm and 13.01Â cm, respectively.
Erect circumference
Similar results exist regarding studies of the circumference of the adult fully erect penis, with the measurement usually taken mid-shaft. As with length, studies that relied on self-measurement consistently reported a significantly higher average than those with staff measuring. In a study of penis size where measurements were taken in a laboratory setting, the average penis circumference when erect was 4.8 inches (12.3Â cm), which means that the average width of the erect penis is approximately 1.5 inches (4Â cm).
Size at birth
The average stretched penile length at birth is about 4Â cm (1.6Â in), and 90% of newborn boys will be between 2.4 and 5.5Â cm (0.94 and 2.17Â 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 6Â cm (2.4Â in) with adult size reached about 5 years later. W.A. Schonfeld published a penis growth curve in 1943.
Size with ageing
Authors of a paper reviewing research on area of penis sizes conclude that "flaccid penile length is just under 4Â cm (1.6Â in) at birth and changes very little until puberty, when there is marked growth."
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]."
Size and height
A 2015 review of the literature found two studies finding height and stretched or flaccid length to be moderately correlated, seven studies finding weak correlation for flaccid, stretched, or erect length, and two studies that found no correlation between flaccid length and height.
Size and race
The belief that penis size varies according to race is not supported by scientific evidence. A 2007 study reported that "there is no scientific background to support the alleged ‘oversized’ penis in black people". Another study noted that contrary to the "popular belief that black people generally have longer penile sizes", in reality "there is no convincing scientific background" to support this idea. A 2015 systematic review found that it was not possible to draw any conclusions about size and race from the available literature and that further research needed to be conducted.
Variance
Genetics
There are certain genes, like homeobox (Hox a and d) genes, which may have a role in regulating penis size. In humans, the AR gene located on the X chromosome at Xq11-12 which may determine the penis size. The SRY gene located on the Y chromosome may have a role to play. Variance in size can often be attributed to de novo mutations. Deficiency of pituitary growth hormone or gonadotropins or mild degrees of androgen insensitivity can cause small penis size in males and can be addressed with growth hormone or testosterone treatment in early childhood.
Conditions
An adult penis with an erect length of less than 7Â cm or 2.76Â inches but otherwise formed normally is referred to in a medical context as having the micropenis condition. The condition affects 0.6% of men. Some of the identifiable causes are deficiency of pituitary growth hormone 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. Operations are also available to increase penis size in cases of micropenis in adults.
Environmental influence
It has been suggested that differences in penis size between individuals are caused not only by genetics, but also by environmental factors such as culture, diet and chemical or pollution exposure. Endocrine disruption resulting from chemical exposure has been linked to genital deformation in both sexes (among many other problems). Chemicals from both synthetic (e.g., pesticides, anti-bacterial triclosan, plasticizers for plastics) and natural (e.g., chemicals found in tea tree oil and lavender oil) sources have been linked to various degrees of endocrine disruption.
Both PCBs and the plasticizer DEHP have been associated with smaller penis size. DEHP metabolites measured from the urine of pregnant women have been significantly associated with the decreased penis width, shorter anogenital distance and the incomplete descent of testicles of their newborn sons, replicating effects identified in animals. Approximately 25% of US women have phthalate levels similar to those in the study.
A 2007 study by the University of Ankara, Faculty of Medicine found that penile size may decrease as a result of some hormonal therapy combined with external beam radiation therapy. In addition, some estrogen-based fertility drugs like diethylstilbestrol (DES) have been linked to genital abnormalities or a smaller than normal penis (microphallus).
Perceptions
Historical
Perceptions of penis size are culture-specific. Ancient Egyptian cultural and artistic conventions generally prevented large penises from being shown in art, as they were considered obscene, but the scruffy, balding male figures in the Turin Erotic Papyrus are shown with exaggeratedly large genitals.
The ancient Greeks believed that small penises were ideal. Scholars believe that most ancient Greeks probably had roughly the same size penises as most other Europeans, but Greek artistic portrayals of handsome youths show them with inordinately small, uncircumcised penises with disproportionately large foreskins, indicating that these were seen as ideal. Large penises in Greek art are reserved exclusively for comically grotesque figures, such as satyrs, a class of hideous, horse-like woodland spirits, who are shown in Greek art with absurdly massive penises. Actors portraying male characters in ancient Greek comedy wore enormous, fake, red penises, which dangled underneath their costumes; these were intended as ridiculous and were meant to be laughed at. In Aristophanes's comedy The Clouds, "Mr. Good Reason" gives the character Pheidippides a description of the ideal youth: "A glistening chest and glowing skin,/Broad shoulders, a small tongue,/A mighty bottom and a tiny prong."
In Greek mythology, Priapus, the god of fertility, had an impossibly large penis that was always permanently erect. Priapus was widely seen as hideous and unattractive. A scholion on Apollonius of Rhodes's Argonautica states that, when Priapus's mother Aphrodite, the goddess of love and beauty, gave birth to him, she was so horrified by the size of his penis, his massive potbelly, and his huge tongue that she abandoned him to die in the wilderness. A herdsman found him and raised him as his son, later discovering that Priapus could use his massive penis to aid in the growth of plants.
Penis size is also alluded to in the Bible:
18When she carried on her whoring so openly and flaunted her nakedness, I turned in disgust from her, as I had turned in disgust from her sister.19Yet she increased her whoring, remembering the days of her youth, when she played the whore in the land of Egypt20and lusted after her lovers there, whose members were like those of donkeys, and whose issue was like that of horses. Ezekiel 23:18â€"20, English Standard Version.
In medieval Arabic literature, a longer penis was preferred, as described in an Arabian Nights tale called "Ali with the Large Member". As a witty satire of this fantasy, the 9th-century Afro-Arab author Al-Jahiz wrote: "If the length of the penis were a sign of honor, then the mule would belong to the Quraysh" (the tribe to which Muhammad belonged and from which he descended).
The medieval Norsemen considered the size of a man's penis as the measure of his manliness, and a thirteenth-century Norse magic talisman from Bergen, a wooden stave inscribed with writing in runic script, promises its wearer: "You will fuck Rannveig the Red. It will be bigger than a man's prick and smaller than a horse's prick." A late fourteenth century account of the life of Saint Ã"láfr from the Flateyjarbók describes a pagan ritual, which centered around a preserved horse's penis used as a cult artifact, which members of the cult would pass around in a circle, making up verses in praise of it, encouraging it and the other members of the group to behave in sexually suggestive ways.
Males may quite easily underestimate the size of their own penis relative to that of others, and many men who believe that their penis is of inadequate size have average-sized penises. The perception of having a large penis is often linked to higher self-esteem. Fears of shrinking of the penis in folklore have led to a type of mass hysteria called penis panic, though the penis legitimately can shrink in size due to scar tissue formation in the penis from a medical condition called Peyronie's disease. Marketers of penis enlargement products exploit fears of inadequacy, but there is no consensus in the scientific community of any non-surgical technique that permanently increases either the thickness or length of the erect penis that already falls into the normal range.
Male self-perception
Males may quite easily underestimate the size of their own penis relative to that of others, because of the foreshortening obtained from looking down, due to repeated observation of atypical penises in pornography, 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. The perception of having a large penis is linked to higher self-esteem.
Among gay men
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. One study analysing the self-reported Kinsey data set found that the average penis of a homosexual man was larger than the average penis of their heterosexual counterparts (6.32Â inches [16,05Â cm] in length amongst gay men versus 5.99" [15,21Â cm] in heterosexuals, and 4.95Â inches [12,57Â cm] circumference amongst gay men versus 4.80" [12,19Â cm] in heterosexual men).
Anxiety
Widespread private concerns related to penis size have led to a number of folklore sayings and popular culture reflections related to penis size. Penis panic is a form of mass hysteria involving the believed removal or shrinking of the penis, known as genital retraction syndrome. The penis can significantly shrink due to scar tissue formation from a condition called Peyronie's disease which affects up to 10% of men. Products such as penis pumps, pills, and other dubious means of penis enlargement are some of the most marketed products in email spam. At present there is no consensus in the scientific community of any non-surgical technique that permanently increases either the thickness or length of the erect penis that already falls into the normal range (4.5" to 7").
Size of other body parts
A statistically significant correlation between penis size and the size of other body parts has not been found in research. One study, Siminoski and Bain (1988), found a weak correlation between the size of the stretched penis and foot size and height; however, it was too weak to be used as a practical estimator. Another investigation, Shah and Christopher (2002), which cited Siminoski and Bain (1988), failed to find any evidence for a link between shoe size and stretched penis size, stating "the supposed association of penile length and shoe size has no scientific basis".
There may be a link between the malformation of the genitalia and the human limbs. 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).
Studies of size preferences among sexual partners
In a small study conducted by University of Texasâ€"Pan American and published in BMC Women's Health, 50 undergraduate women were surveyed by two popular male athletes on campus about their perceptions of sexual satisfaction and it was concluded that the width of a penis feels better than the length of a penis, when subjects are asked to choose between the two (size was left unspecified). It was also concluded that this may show that penis size overall affects sexual satisfaction since women chose between the two options they were given.
In a cover story by Psychology Today, 1,500 readers (about two-thirds women) were surveyed 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. Generally, the women polled cared more about width than men thought, and less about length than men thought, although the strength of caring for either among women showed a similar pattern.
Another study, conducted at Groningen University Hospital, asked 375 sexually active women (who had recently given birth) the importance of penis size the results of which showed that 21% of women felt length was important and 32% felt that girth was important.
A study conducted at the Australian National University, published in early 2013, showed that penis size influences a man's sex appeal, and the taller the man, the bigger the effect. The study showed 3D computer generated images at life size, altering the height and other physical attributes, with women typically registering preferences in under 3 seconds. A preference for taller men's larger penis size was notable.
A U.S. study published in 2015 of the stated preferences of a panel of 75 women using 3D-printed models as scale references showed a preferred penis length of 16Â cm and a preferred circumference of 12.2Â cm for long-term sexual partners, with slightly larger preferred sizes of a length of 16.3Â cm and circumference of 12.7Â cm for one-time sexual encounters.
The term size queen is slang for anyone who prefers their sexual partner(s) to have a larger-than-average penis.
Evolution
The human penis is thicker than that of any other primate, both in absolute terms and relative to the rest of the body. Early research, based on inaccurate measurements, concluded that the human penis was also longer. In fact, the penis of the common chimpanzee is no shorter than in humans, averaging 14.4Â cm (5.7 inches), and some other primates have comparable penis sizes relative to their body weight.
The evolutionary reasons for the increased thickness have not been established. One explanation is that thicker penises are an adaptation to a corresponding increase in vaginal size. The vaginal canal is believed to have expanded in humans to accommodate the larger size of a newborn's cranium. Women may then have sexually selected men with penises large enough to fit their vagina, to provide sexual stimulation and ensure ejaculation.
Condom use
One Australian study of 184 men looked at penis length and circumference in relationship to condom breakage or slippage. 3,658 condoms were used. The study found that when used correctly, condoms had a breakage rate of 1.34% and a slippage rate of 2.05%, for a total failure rate of 3.39%. Penile dimensions did not influence slippage, but penis circumference and broken condoms were strongly correlated, with larger sizes increasing the rate of breakage.
See also
- Digit ratio
- Human vaginal size
- Jonah Falcon
- Penis envy
- Phalloplasty
- Sexual selection in human evolution
- The Third Chimpanzee
- Why Is Sex Fun?
References
- Notes
- Sources
- EurekAlert! summary
- Lee, P.; Mazur, T.; Danish, R.; Amrhein, J.; Blizzard, R.; Money, J.; Migeon, C. (1980). "Micropenis. I. Criteria, etiologies and classification". The Johns Hopkins medical journal. 146 (4): 156â€"163. PMID 7366061.Â
- Lauersen, Niels; Whitney, Steven (1983). It's Your Body: A Woman's Guide to Gynecology (3rd ed.). New York: Berkley Publishing. p. 480. ISBN 0-425-09917-2.Â
- Rushton, J.; Bogaert, A. F. (1987). "Race differences in sexual behavior: Testing an evolutionary hypothesis*1". Journal of Research in Personality. 21 (4): 529â€"551. doi:10.1016/0092-6566(87)90038-9.Â
- Sutherland, RS; Kogan, BA; Baskin, LS; Mevorach, RA; Conte, F; Kaplan, SL; Grumbach, MM (1996). "The effect of prepubertal androgen exposure on adult penile length". The Journal of Urology. 156 (2 Pt 2): 783â€"7; discussion 787. doi:10.1016/S0022-5347(01)65814-2. PMID 8683783.Â
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