Micropenis is an unusually small penis. A common criterion is a dorsal (measured on top) erect penile length of at least 2.5 standard deviations smaller than the mean human penis size, or smaller than about 7 cm (2 3⁄4 in) for an adult when compared to an average erection of 12.5 cm (5 in).The condition is usually recognized shortly after birth. The term is most often used medically when the rest of the penis, scrotum, and perineum are without ambiguity, such as hypospadias. Micropenis occurs in about 0.6% of males.