Human penis size is the measured length and width of the
human penis. The most accurate measurement of the human penis comes from several measurements at different times, as there is natural variability in size due to arousal level, time of day, room temperature, frequency of sexual activity, and unreliability of the measurement methods. When compared to other primates, including large
primates such as the
gorilla, the genitalia of male humans are large, both in absolute terms and in relative size to the rest of the body. Results vary, with studies that rely on self-measurement reporting a significantly higher average than those with staff measuring, but a
mean human penis is approximately 12.915
cm (5.15.9
in) in length. Flaccid penis length is a poor estimate of
erect length. Most of human penis growth happens between infancy and the age of five, and in five years after the onset of
puberty. There is evidence both for and against a link between penis size and the size of other body parts. Some environmental factors in addition to genetic, such as the presence of
endocrine disruptors, can affect penis growth. 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.
Perceptions of penis size are culture-specific. In
Ancient Greece and in
Renaissance art, 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.
Ancient Rome may have had a contrary view, and a larger penis size was preferred in medieval
Arabic literature. 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 linked to higher self esteem in general, but also among
gay men specifically. For women, width rather than length is a more important factor of sexual stimulation. Fear of shrinking of the penis in folklore have led to a type of
mass hysteria called
penis panic. 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.