What Changes to Expect in Boys During Puberty
Published November 14, 2026 · Written from AAP, KidsHealth and other pediatric sources
Boys do better when they know what is coming. Here is a parent-friendly rundown, drawn from KidsHealth, the AAP and pediatric hospital guides.
The main changes
- Growth of the testicles and penis. The AAP says the penis grows first in length, then in width. A boy may have adult-size genitals as early as 13 or as late as 18.
- Hair. Boys get pubic and underarm hair, leg hair becomes thicker and darker, and facial hair appears.
- Acne and sweat. KidsHealth says both boys and girls often get acne and start to sweat more.
- Growth spurt. Muscles get bigger as boys shoot up in height.
- Voice. KidsHealth describes the voice cracking and then deepening.
- Erections and wet dreams. KidsHealth says erections can happen at any time and even in sleep, and that wet dreams are possible.
The ones that surprise parents
Temporary breast tissue
KidsHealth says some boys have temporary breast growth during puberty, called gynecomastia, caused by changing hormone levels. It usually goes away, often within a few months to a couple of years.
Looking chubby and gangly
The AAP notes that boys tend to look a little chubby and gangly (long arms and legs compared to the trunk) just before and at the start of puberty.
Size worries
The AAP says the number one concern for boys is size, and that boys spend a lot of time comparing. A helpful line from the AAP for parents is that many boys worry their penis is too small, and that this almost never turns out to be the case. KidsHealth adds that penises come in different sizes and shapes, with less difference in size when erect.
Different timing is normal
Valley Children's suggests telling your child that kids of the same age may be at different stages of puberty. KidsHealth notes an early or late bloomer may feel awkward or like classmates are staring, so reassurance helps.
Good to know: This article is general education, not medical advice. If you are worried about your son's health or development, ask his pediatrician.
Sources
- Talking to Your Child About Puberty (KidsHealth, Nemours)
- Boys and Puberty (KidsHealth, Nemours)
- Physical Development in Boys: What to Expect (HealthyChildren.org, American Academy of Pediatrics)
- Puberty: Normal Growth and Development in Boys (Valley Children's Healthcare)
Facts checked against these pages on November 14, 2026. See how we fact-check.