Stages of Physical Development in Adolescence


A man holding a birthday cake

Puberty starts when changes in your child’s brain cause sex hormones to start being released in girls’ ovaries and boys’ testes. This usually happens around 10-11 years for girls and around 11-13 years for boys. But it’s normal for the start of puberty to range from 8-13 years in girls and 9-14 years in boys. Every child is different.

Physical Development in Adolescent Girls

A little girl lying on a bed

If you have a daughter, these are the main external physical changes in puberty that you can expect.

Around 10-11 years

  • Breasts will start developing. This is the first visible sign that puberty is starting. It’s normal for the left and right breasts to grow at different speeds. It’s also common for the breasts to be a bit tender as they develop. If your child wants a bra, a soft crop top or sports bra can be a good first choice.
  • Your daughter will have a growth spurt, and she’ll get taller. Some parts of her body – like her head, face and hands – might grow faster than her limbs and torso. This might leave her looking out of proportion for a while. On average girls grow 5-20 cm. They usually stop growing at around 16-17 years.
  • Your daughter’s body shape will change. For example, her hips will widen.
  • Your daughter’s external genitals (vulva) and pubic hair will start to grow. Her pubic hair will get darker and thicker over time.

Around 12-14 years 

  • Hair will start growing under your daughter’s arms.
  • Your daughter will get a clear or whitish discharge from her vagina for several months before her periods start. If the discharge bothers your daughter, you could suggest she uses a panty liner. If your daughter says she has itching, pain or a bad or strong odour, check with a GP.
  • Periods will start. This is when the lining of the uterus (womb), including blood, is shed every month. Your daughter might get pain before and during her period, like headaches or stomach cramps. Her periods might be irregular at first.

Physical Development in Adolescent Boys

A woman talking on a cell phone

If you have a son, these are the main external physical changes in puberty that you can expect.

Around 11-13 years

  • The external genitals (penis, testes and scrotum) will start to grow. It’s normal for one testis to grow faster than the other. You can reassure your son that men’s testes usually aren’t the same size.
  • Pubic hair will start to grow. It will get darker and thicker over time.

Around 12-14 years

  • Your son will have a growth spurt. He’ll get taller and his chest and shoulders will get broader. Some parts of his body – like his head, face and hands – might grow faster than his limbs and torso. This might leave him looking out of proportion for a while. On average boys grow 10-30 cm. They usually stop growing at around 18-20 years.
  • It’s common for boys to have minor breast development. If your son is worried by this, you can let him know it’s normal and usually goes away by itself. If it doesn’t go away or if your son’s breasts seem to be growing a lot, he could speak to his GP.

Around 13-15 years

  • Hair will start growing on other parts of your son’s body – under his arms, on his face and on the rest of his body. His leg and arm hair will thicken. Some young men will grow more body hair into their early 20s.
  • Your son will start producing more testosterone, which stimulates the testes to produce sperm.
  • Your son will start getting erections and ejaculating (releasing sperm). During this period, erections often happen for no reason at all. Just let your son know that this is normal and that people don’t usually notice. Ejaculation during sleep is often called a ‘wet dream’.

Around 14-15 years
The larynx will become more obvious. Your son’s larynx will get larger and his voice will ‘break’, eventually becoming deeper. Some boys’ voices move from high to low and back again, even in one sentence. This will stop in time.

These are some obvious stages of physical development in adolescence.

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