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How breasts develop during puberty

Girls usually start to develop breasts between the ages of 9 and 11. Breasts come in all different shapes and sizes. Find out more about how breasts develop and where to get more support.

1. What age do breasts fully develop?

Breasts usually start to develop around the age of 9 to 11, but it’s normal for them to start earlier or later.

If a girl’s breasts start to develop at a younger age, this doesn’t mean she’ll have bigger breasts than someone who starts to develop later. The rate at which breasts grow is different for everyone.

2. How do breasts start to develop?

When breasts start to develop, a small bump called a breast bud grows under the nipple and .

The breasts get bigger and rounder as the fatty tissue and milk-producing glands inside the breasts continue to grow. The areola also gets bigger and darker and the nipples may stick out.

By the age of 17, a girl’s breasts will usually be fully developed, although this may take a bit longer.

You’ll probably notice that you and your friends grow in different ways. One girl’s breasts may start to develop first, but her friend may get her period earlier. Bodies don’t develop in any set order and everyone’s different.

Aching, itching or tender breasts

As the breast buds grow, you may notice tingling, aching or itching in your chest, and your nipples may swell or become tender. This is all normal.

After your periods begin, the changing hormones may make the breasts feel tender, painful or sore a week or so before your period starts.

3. Are my breasts normal?

It's common to worry about whether your breasts are normal.

But normal breasts come in different sizes and shapes and everyone's breasts are different.

Find out more about normal breasts and nipples.

4. Can I change the way my breasts develop?

There’s nothing you can do to speed up or slow down breast development.

Creams and pills

Adverts for creams and pills often claim that they can make breasts bigger or smaller. These creams and pills don’t usually make any difference to breast size – even if there’s a slight change in size it’s unlikely to last.


Massaging the breasts won’t affect their size. Massaging too hard might even hurt the breasts or irritate the skin and nipples.


Breasts are mainly made up of fatty tissue rather than muscle, so exercise won’t affect breast development. However, exercise in general will help keep the pectoral muscles behind the breast in shape, as well as help toning the body. It’s important to wear a sports bra that fits you well and supports your breasts during exercise.

Gaining or losing weight

Losing or putting on weight may affect breast size, but doesn’t always.

Sometimes girls put on weight during puberty. This is normal and it’s essential to have some body fat. Because breasts contain fatty tissue, gaining weight may increase the size of the breasts, and losing weight may make the breasts a bit smaller.

Sleeping on your front

Sleeping on your front won’t affect how your breasts develop or make them smaller. If your breasts are feeling sore you might find it more comfortable to sleep on your back or side.

Wearing a bra to sleep in

Whether you sleep with or without a bra is a personal choice, but neither will affect breast development. If you do sleep in a bra, make sure it’s comfortable and not too tight.


Cosmetic breast surgery is the only way to alter breast size – through either a breast enlargement with implants or breast reduction.

Breast enlargement or reduction surgery is available only to people over the age of 18, and may not be funded by the NHS. Surgery has potential risks and side effects – for example scar tissue and infection, reduced sensitivity and not being able to breastfeed.

5. Further support

Changes to your body during puberty can make you feel anxious or like you don’t have control.

If you’re finding it difficult to cope, talk to your GP, or you can talk to one of our experts via our free helpline. See the bottom of this page for more information. 

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Quality assurance

Last reviewed in February 2019. The next planned review begins in February 2023.

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