|Typical testicle volume and fertility||Penis
|Artist's impression of genitalia (when loosely circumcised)||Annual height gain||Comments|
|Stage 1||Under 4 ml
Not fertile at least whilst orgasms, if any, remain dry.
|Erections occur spontaneously or by masturbation.
Tight circumcision produces a much shorter shaft that is horizontal when flaccid.
|50 - 60 mm||If elective circumcision is chosen on parental initiative, it is best done no later than Tanner Stage 1.
|Mean age (and 'normal' range) at stage boundary:  11.5 (9.5 to 13.5) years|
|Stage 2||6 ml
Fertility normally begins during this stage.
|First discernible increase in both length and girth. The erect penis may carry at a very high angle, almost touching the abdomen.||50 - 60 mm||First growth of pubic hair that is evidently different from other body hair. Occasional ejaculation now becomes possible by masturbation.|
|Mean age (and 'normal' range) at stage boundary:  12.4 (10.1 to 14.6) years|
|Stage 3||14 ml
|Growth continues in both length and girth, partly recovering any shortening that resulted from tight circumcision before puberty.||70 - 80 mm||Voice breaks. Ejaculation occurs more frequently in wet dreams or by masturbation. This is beneficial in terms of long-term prostate health.|
|Mean age (and 'normal' range) at stage boundary:  14.0 (11.5 to 16.5) years|
|Stage 4||20 ml
|-- Ditto --||Peaks circa 100 mm||Voice matures.
Underarm hair develops.
Wet dreams frequent in the absence of other sexual activity.
|Mean age (and 'normal' range) at stage boundary:  16.5 (14.5 to 18.5) years|
|Stage 5||28 ml
Modern society tends to defer fatherhood to a later age, but in biological terms this is the lifetime peak of fertility.
|Mature size in terms of both length and girth (flaccid and erect) is reached typically five years after crossing the Stage 1 - Stage 2 boundary.||Growth ceases typically six years after crossing the Stage 1 - Stage 2 boundary.||Adult pubic hair distribution.
General adult physique and sexuality.
- Artwork credit: J. Geoff Malta, MA, EdM
- Parents wishing to convey the above information to boys approaching puberty will find a simplified, more child-oriented version here: http://www.puberty101.com. The same website also gives age-appropriate information about puberty in girls.
- Age boundaries have been adjusted from Tanner's original (1960s) work to account for a modern tendency towards earlier puberty. The reasons for this trend are not fully understood.