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Puberty information for boys and girls

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  • Puberty brings about physical and emotional changes in your body. These are a natural part of growing up and are nothing to worry about.
  • Puberty usually starts between 9 and 16 – exactly when varies from person to person, but girls often start younger than boys.
  • During puberty you may start thinking about sex. This is perfectly normal but make sure both you and your partner are ready, and that you understand how to avoid unwanted pregnancy and prevent HIV and other sexually transmitted infections.  

As you start to become an adult, your body goes through lots of changes. From growing body hair to starting your periods, find out what to expect when you go through puberty.

What is puberty?

Puberty is when your body starts to develop and change, showing that you are becoming an adult. These changes are very normal and part of growing up. As well as physical changes, you may also start to have sexual feelings and notice your moods and emotions changing, too.

When does puberty start?

There is no set age for puberty so try not to worry if your body changes earlier or later than your friends’ bodies. For girls, puberty often happens between 9 and 15. Boys usually start puberty between 11 and 16.

These changes happen over several years. Everyone’s body is different – some people develop very quickly and others more slowly. It’s also normal for different changes to happen in your body at different times to your friends.

Puberty in girls – what are the stages and changes to the body?

Sex organs

One of the main physical changes of puberty is the growth and development of the sex organs – used to have sex and make babies.

During puberty your vagina changes and starts to produce a clear or milky liquid called discharge. It may seem strange at first but it’s a good sign as it helps to keep your vagina healthy.

Female stages of puberty


Your nipples and breasts will start to fill out during puberty. Breasts grow into a variety of shapes and sizes – big, small, large nipples, hair around the nipples – all are normal.

All my friends wear bras every day but I don't know if I am ready to wear a bra yet. My mum says 'Your breasts are developing', but they are really small! I only have two bras so far, and when I wear them I feel like my breasts are fake because they are padded ones. I hope soon that I will feel self-confident about who I am - Elin

It’s also normal for one breast to grow faster than the other. Usually breasts become more even as they reach full development, but most breasts will always be slightly uneven in shape and size.

Female stages of puberty - breast development


One of the biggest changes for girls is their periods starting. While the average age for periods to start is 12, many girls experience them earlier and lots don’t get them until later.

Periods show that your body can now have a baby. Each month one of your ovaries releases an egg, which can be fertilised by a boy’s sperm to create a pregnancy. If the egg isn’t fertilised, the lining of the womb breaks down, creating the blood that passes through your vagina during your period.

Periods generally happen every 28 days, and last between three and five days – but this varies for different women. Most girls use cloth, towels or tampons to absorb the blood and protect clothing.

Other changes for girls

  • Hair grows under your arms and between your legs. Your leg hair may get thicker and darker and you may grow hair on your upper lip.
  • Your hips will start to broaden. This is preparing your body to be able to have babies.
  • Many girls start to get spots.
  • It’s normal to sweat more and many girls start to use deodorant.
  • Rapid growth spurts may happen from time to time.

Puberty in boys – what are the stages and changes to the body?

Sex organs

As a boy goes through puberty his penis grows thicker and longer, and his testicles move lower down his scrotum (ball sack). Sometimes one testicle grows faster than the other, and it is natural for one to hang lower than the other.

Male stages of puberty

Erections and ejaculation

It’s usual to start getting more erections – when your penis temporarily grows and hardens – at odd times, often when you aren’t thinking about sex. Erections are normal and happen when sponge-like tissue inside your penis fills up with blood – as a result of messages sparked from your brain (from a smell, touch, sight, or sound).

You might also have 'wet dreams' – when you ejaculate in your sleep. Ejaculations are the way your body pushes out semen (sperm and other fluids) through your penis. If the sperm in the semen meets a girl’s egg it can fertilise the egg to create a pregnancy.

Other changes for boys:

  • Pubic hair starts to grow at the base of your penis and lower abdomen, on your scrotum, and under your armpits.
  • You start growing facial hair – how much and how soon varies a lot.
  • Your voice starts to get deeper, also known as ‘breaking’. For some boys this happens quickly and for others it takes time.
  • It’s normal to sweat more and many boys start to use deodorant.
  • Many boys start to get spots.
  • Rapid growth spurts may happen from time to time.

What if I don’t fit ‘girl’ or ‘boy’?

Lots of people don’t fit simply into the category ‘girl’ or ‘boy’ – whether that is physically, biologically or emotionally.

You may think you are transgender – where you have a girl’s body but feel like a boy, or the other way around. Or you may feel you don't fit into the confines of being exclusively male or female (non-binary). Or you may think you are intersex – where your sex organs don’t fit typical male or female characteristics.

If you are experiencing any of these, you may find the information on the Advocates for Youth site, the AIS-DSD intersex support group, and the InterACT Youth site useful.

New feelings and emotions

It’s perfectly normal to start thinking about sex a lot more during puberty. Many people start to explore and touch their bodies (called masturbation). It may seem strange at first, but masturbation is a very natural way to make yourself feel good and is nothing to be ashamed of.

Some people start becoming attracted to people of the same gender, the opposite gender, or both during puberty. Others may not be attracted to anyone. This is perfectly normal, and you shouldn't worry about it. Some people discover their sexuality when they are very young, during puberty or when they are much older – this is fine too.

Taking control of your sexual health

When you think you are ready to start exploring sex, make sure you understand how to avoid unwanted pregnancy and prevent HIV and other sexually transmitted infections (STIs).

Remember that sex must always be with your consent and you should never feel pressured into doing anything you don’t want to. It’s also fine to ask the person you are with to stop at any point if you’re no longer feeling comfortable.

Getting support if you need it

Reaching puberty and growing up can be an exciting time, but it may sometimes bring difficult thoughts and feelings too.

If you’re experiencing mood swings or feeling aggressive or depressed it often helps to talk to someone you trust, such as a friend or relative. If you need more support, it may also help to contact a healthcare professional or a helpline.

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Photo credit: ©  Photos are used for illustrative purposes. They do not imply any health status or behaviour on the part of the people in the photo.

Photo credit: © Luzzatti Buyé
Photo credit: © Luzzatti Buyé
Last full review: 
29 June 2021
Next full review: 
29 June 2024
Last updated:
11 October 2021
Last full review:
29 June 2021
Next full review:
29 June 2024