Tanner Stages of Puberty

The Tanner Scale is a physical reference for the stage a boy or girl is in from prepubescence to pubescence to adolescence to adulthood.

For boys, it references penis size, testicle size, and scrotum size and color. It also references the growth of pubic hair.

The first stage: prepubertal (before puberty) boy's penis is small. There is no pubic hair yet.

The second stage: the testicles enlarge a little, the scrotum becomes thinner, larger, and turns redder; the penis is the same length as the first stage, and there is some hair right above the penis.

The third stage: the testicles and scrotum grow; the penis becomes longer. There is more curly pubic hair.

The fourth stage: the testicles and scrotum grow; the scrotum becomes darker. The penis increases in length and width, and there is more pubic hair.

The fifth stage: the testicles, scrotum, and penis are fully grown. Pubic hair is fully grown and grows to the thighs. Males stop growing and reach their adult height.