human penis size human penis size human penises vary in size on a number of measures, including length and circumference when flaccid and erect. besides the natural variability of human penises in general, there are factors that lead to minor variations in a particular male, such as the level of arousal, time of day, ambient temperature, anxiety level, physical activity, and frequency of sexual activity. 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. most human penis growth occurs in two stages: the first between infancy and the age of five; and then between about one year after the onset of puberty and, at the latest, approximately 17 years of age. "penis length" and "small penis" redirect here. for differences in penis length among non-human species, see penis § in different animals. for the medical term, see micropenis. diagram showing how to measure the length and circumference of an erect human penis 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 15,521 men, who were measured by health professionals rather than themselves, concluded that the average length of an erect human penis is 13.12 cm (5.17 inches) long, while the average circumference of an erect human penis is 11.66 cm (4.59 inches). a 1996 study of flaccid length found a mean of 3.5 inches (8.9 cm) when measured by staff. flaccid penis length can sometimes be a poor predictor of erect length. an adult penis with an erect length of less than 9.3 cm (3.7 in), but otherwise formed normally, is referred to in medicine as a micropenis.a human penis, flaccid and erect. flaccid length is a poor predictor for erect length. limited to no statistically significant correlation between penis size and the size of other body parts has been found in research. some environmental factors in addition to genetics, such as the presence of endocrine disruptors, can affect penis growth. studies distribution of penis sizes by length. 45% of erect penises are between 12 and 14 cm long. distribution of penis sizes by circumference. 81% of erect penises (green) are between 10 and 13 cm in circumference. percentile of penile length percentile of penile circumference while results vary slightly across reputable studies, the consensus is that the mean human penis, when erect, is in the range 12.9–15 cm (5.1–5.9 in) in length. mean erect length with measurements adult male erection in the mean range, measuring 14 centimetres (5.5 in) 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 9.16 cm, 13.24 cm, and 13.12 cm respectively, and mean flaccid and erect circumferences of 9.31 cm and 11.66 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. flaccid one study (published in 1996) 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 9–10 cm (3.5–3.9 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, anxious or nervous level and participation in sports. this decrease of flaccid penis size is referred to by the slang term "shrinkage", due to action by the cremaster muscle. the same phenomenon affects cyclists 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). individuals with hard flaccid syndrome or other pelvic floor disorders may temporarily have an abnormally small penis. 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. one study found that a minimal tension force of approximately 450 g during stretching of the penis was required to reach a full potential erection length. this study also found that tension forces exerted in this study by the urologist were shown to be significantly (p<0.01) lower than 450g. this may account for differences between stretched and erect length. the 2015 study of 15,521 men found that the average length of a stretched flaccid penis was 13.24 cm (5.21 inches) long, which is near identical to the average length of an erect human penis which is 13.12 cm (5.17 inches) long. an 2001 study of about 3,300 men published in european urology concluded that flaccid stretched length was measured on average to about 12.5 cm (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, −0.140 with weight, and −0.238 with bmi, flaccid circumference and height 0.156, stretched length and height 0.221, weight −0.136, bmi −0.169. they also reported a few non-significant correlations. 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 (in other words, 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 12.9 cm (5.1 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). the study intended "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 (ed) (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 14–16 cm (5.5–6.3 in) and girth to be 12–13 cm (4.7–5.1 in). the paper compared results of twelve studies conducted on different populations in several countries. various methods of measurements were included in the review. a 2015 study by bju international concluded the average erect penis length to be 13.12 cm (5.16 inches). a 2013 study of 253 men from tanzania found that the average erect penis length of tanzanian males was 13.12 cm (5.17 inches) an indian study (published in 2007) of 301 men ages 18 to 60 published in the international journal of impotence research found flaccid, stretched and erect length to be 8.21 cm (3.23 in), 10.88 cm (4.28 in) and 13.01 cm (5.12 in), respectively. a korean study (published in 1971) of 702 men ages 21 to 31 identified the average erect penis length to be 12.70 cm (5.00 in). another study (from 1998) of 150 koreans found the average erect penis length to be 13.42 cm (5.28 in). the most recent study (published in 2016) of 248 korean men identified the average erect penis length to be 13.53 cm (5.33 in). a 2020 review in the journal of sex & marital therapy found that the majority of men believed that the average erect penis length is more than 15.24 cm (6 inches). this inaccurate belief has likely been fed by inaccurate and exaggerated data presented in studies where the size of a participant's erect penis is self-reported. participants may report overestimates of the size of their penis in the belief that a larger penis is more socially desirable. the same review analyzed the results from ten prior studies where measurements of erect penis size were made by researchers. they reported an erect penis to be between 12.95 and 13.92 cm (5.1 and 5.5 inches, respectively) in length, a result significantly below the average obtained in self-reported studies. the authors commented that results of such measurement studies may still be inflated due to volunteer bias – the possibility that men with larger penises may be more likely to choose to participate in such studies. 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 11.66 cm (4.59 inches). 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 (0.94 and 2.17 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 ageing authors of a paper reviewing research on area of penis sizes conclude that "flaccid penile length is just under 4 cm (1.6 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 ." 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 hands one study investigated the relationship with digit ratio and found that men with longer ring fingers than index fingers had slightly longer penises. however, the common misconception that hand size predicts penis size has been widely discredited. size and other body parts 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". a study by ikegaya et al. (2021) concluded that nose size was highly related to stretched penile length in japanese male cadavers. 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). size and race alleged differences in races have led to the creation of sexual myths. a 2005 study reported that "there is no scientific background to support