Puberty for boys

What it is

In boys, puberty usually starts between ages 9 and 14, about two years after girls.¹ The main driver is testosterone, made by the , which brings on height and muscle growth, body and pubic hair, a deeper voice and genital growth.² It usually lasts two to five years and ends around 16 or 17.¹

The order

Testicles first. Usually between 9 and 14. The and grow, and a little hair appears around the penis and under the arms. Sweat starts to smell.¹
Things speed up. Usually between 10 and 16. The penis grows, pubic hair gets thicker, muscles grow and the voice starts to crack and deepen. Wet dreams, releasing semen during sleep, may start.¹ From now on the testicles can keep making sperm for life.³
The biggest growth spurt. Usually between 11 and 16, averaging nearly 10 cm (4 inches) a year at its peak. Body hair reaches adult levels and acne is common.¹
The finish. Facial hair often doesn't fill in until this last stage. Most boys finish growing by about 17, though some grow into their early 20s.¹

Common, and normal

Breast swelling. About half of boys get some swelling of breast tissue, called gynecomastia, most often between 11 and 15. It usually goes away by the end of puberty. If it hurts or is upsetting, a doctor can help.¹
Voice cracks. The voice can crack for a while as it deepens.¹
Growing pains. Fast growth can bring aches.¹
Moods. Hormone surges and social pressure can bring mood swings and arguments at home, just as for girls.¹

Why boys should learn about periods

Periods are part of life for many of the people boys grow up with: sisters, friends, classmates, and later partners, coworkers and maybe their own children. UNICEF advises talking about periods with boys as a normal part of puberty, not a secret, and making clear that teasing about periods hurts.⁴ It matters: in a 2025 UK survey, half of women said someone had dismissed their period symptoms, and male family members and partners were among the people most often named.⁵

When to see a doctor

Talk to a doctor if:¹

signs of puberty start before 9
there are no signs of puberty by 15
breast swelling hurts, or causes problems at school or with friends
moods include strong anxiety, sadness or anger that doesn't pass

Recap

Boys' puberty usually starts between 9 and 14, about two years after girls', and is driven by testosterone.
The testicles and scrotum grow first. Body hair, a deeper voice, muscle and the biggest growth spurt follow.
Wet dreams and breast swelling are common and normal. The swelling usually goes away by the end of puberty.
See a doctor if signs start before 9, or there are no signs by 15.
Boys should learn about periods too, and girls about boys' puberty.

Words to know 5

gynecomastia	Swelling of breast tissue in boys or men. It is common in puberty and usually goes away.
scrotum	The pouch of skin that holds the testicles.
testicles	The two organs in the scrotum that make sperm and testosterone.
testosterone	The main androgen. In boys it is made by the testicles and drives most changes of puberty.
wet dream	Releasing semen during sleep. Doctors call it a nocturnal emission.