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, room temperature, anxiety level, sport 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. 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). Flaccid penis length can sometimes be 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.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.
It will be bigger than a mans prick and smaller than a horses prick." A late fourteenth century account of the life of Saint Óláfr from the Flateyjarbók describes a pagan ritual which centered around a preserved horses 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.During the Renaissance, some men in Europe began to wear codpieces, which accentuated their genitals. There is no direct evidence that it was necessarily worn to enhance the apparent size of the wearers penis, but larger codpieces were seen as more fashionable. Contemporary perceptions
Male self-perception
Males may quite easily underestimate the size of their own penis relative to those of others. 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 study found that almost all of their patients that were concerned about their penis size overestimated the average penis size. The perception of having a large penis is often linked to higher self-esteem.