As with girls, all boys develop at their own rate - so don't panic if your son seems to be developing earlier or later than his friends. See your doctor if there is no sign of testicular development by the time they are 14, or if they started puberty more than 5 years ago but the penis and the testicles haven't reached full adult development.
These are the Tanner stages of puberty for boys:
Stage one: This is the stage before puberty when boys start to get taller - they'll be growing by 5-6cm per year.
Stage two: Boys usually reach this stage at about 12 - the scrotum thins and reddens, testicles get bigger and fine pubic hair appears at the base of the penis. Their body fat usually decreases too.
Stage 3: The penis grows and lengthens - testicles continue to grow and pubic hair becomes thicker and curlier. They'll also still be getting taller - now growing 7-8cm per year. Their breasts swell slightly, the voice breaks and they might have wet dreams. Boys reach this stage at around 13.
Stage four: At around 14-years-old, they get taller at the fastest rate - growing up to 10cm in one year. The penis and testicles also continue to grow and the scrotum darkens. They start to get underarm hair.
Stage 5: Once they're around 15 the genitals look like an adult's and pubic hair spreads to inner thighs. They're not growing as fast anymore and stop getting taller by about 17. They might still grow more muscle after this and will reach full maturity between 18-19-years-old.
Other physical changes
- During puberty a boy's face lengthens
- He begins to get facial hair
- He starts to sweat more
- His muscles will develop and his chest will broaden
- His skin gets more oily, which means he's likely to get spots or acne