Answers to common questions about boys' bodies, including puberty, sex, penis size and unexpected erections.
Puberty can be a confusing time, because your body and your feelings are changing as you grow up. Here are answers to some of the questions that boys often ask about their bodies.
Click on the questions to go directly to the answer.
At what age do you go through puberty?
Puberty describes all the physical changes that children go through as they grow into adults. Most boys start to go through puberty when they're around 13 or 14 years old, but there's no right or wrong time. It might be sooner or it might be later, and this is normal.
Read more on boys and puberty.
What's the average penis size?
Penis size varies, in the same way that everyone is a different height, weight and build.
Most men's penises are somewhere around 9cm (3.75in) long when not erect, but it's normal for them to be shorter or longer than this. Some things can make your penis temporarily smaller, such as swimming or being cold.
Research has found the average erect penis size varies from around 13cm to 18cm (5in to 7in). You cannot make your penis larger or smaller with exercises or medication.
Find out more about penis size.
What is circumcision?
Circumcision is an operation to remove the piece of skin (the foreskin) that covers the tip of the penis. In the UK, it's usually done for religious reasons, and is most common in the Jewish and Muslim communities. If you've been circumcised, it's nothing to worry about. It won’t affect your ability to have sex.
Female genital mutilation (also called female circumcision or FGM) is illegal in the UK. It involves cutting off some or all of a girl’s external genitals, such as the labia and clitoris.
I have spots on my penis and it itches. Is this normal?
Lots of boys have normal lumps and bumps on their penis, and spots can also be caused by an allergy or irritation. But if you're worried, seek advice from a doctor or clinic. Medical people see problems like this every day, so there's nothing to be embarrassed about.
If you've recently had sex without using a condom, you may have picked up a sexually transmitted infection (STI). Visit a sexual health or genitourinary medicine (GUM) clinic, GP, nurse, young people’s clinic or a community contraceptive clinic.
Find a sexual health clinic near you.
Is it normal for my penis to smell fishy and have white bits behind the tip?
This can happen from time to time. To prevent it, wash gently behind the foreskin if you have one (boys who have been circumcised don’t have a foreskin) when you bath or shower. Use water, or water and a mild soap. Read more about washing your penis.
If you're washing carefully and the symptoms don't go away, and you've had sex without a condom, you may have an STI. See a doctor, or visit a sexual health or GUM clinic, young people’s sexual health or community contraceptive clinic. Find a sexual health clinic near you.
What is sperm?
Sperm is produced in the testicles (balls) and released in fluid called semen during sexual activity. Every time you ejaculate (come) you can produce more than 100 million sperm. But it only takes one sperm to get a girl pregnant, and that can happen before the boy ejaculates. This is because the fluid that comes out of the tip of his penis before ejaculation (called pre-ejaculatory fluid) can contain sperm.
If you're having sex with a girl, always use contraception and condoms to prevent both pregnancy and STIs. Talk to your partner about what contraception she's using, and make sure that you use condoms as well.
If you’re having sex with a boy, always use condoms to stop yourself getting an STI or passing one on.
Is it normal to get an erection when you wake up in the morning?
Yes, most boys have an erection when they wake up in the morning. They can also get one when they're not expecting it during the day, even when they’re not sexually excited. This is a normal part of sexual development and growing up.
Is it normal for one testicle to hang lower than the other?
Yes, this is normal and nothing to worry about. One theory is that it stops your testicles banging together when you run.
How do I know if I have testicular cancer?
Check your testicles every month by gently rolling them, one at a time, between your thumb and fingers to feel for any unusual lumps or bumps. You’ll feel a hard ridge on the upper back of each ball. This is the epididymis, where sperm is stored, and it’s normal to feel it here.
If you feel any lumps, it probably isn’t testicular cancer, but get it checked by a doctor anyway. Other warning signs include:
- one ball growing larger or heavier than the other
- an ache in your balls
- bleeding from your penis
If you notice any of these, see your doctor. If caught early, testicular cancer can usually be treated successfully.
What is premature ejaculation?
This is when a boy or man ejaculates (comes) too quickly during sex. It is fairly common, especially among younger men, and can be due to nerves or over-excitement. Some people don’t worry about it, and some find that using a condom can help to delay ejaculation. Read more about premature ejaculation.
If it bothers you, see your local doctor or nurse, or visit a sexual health or GUM clinic, young people’s clinic or community contraceptive clinic. These places will give you free and confidential advice whatever your age, even if you're under 16. Find a GP or sexual health clinic near you.
Can you pee while having sex?
No. During sex, a valve shuts the outlet tube from your bladder, so that only sperm can pass through the tube (urethra), which you use to pee.
Why is it harder to ejaculate when you have sex a second time soon after the first?
If you have sex a second time straight after the first, it can take longer for you to reach orgasm (come). This is normal. If you're worried, take a longer break after sex before you start again. Whether it's the first, second or tenth time you've had sex that day, always use a new condom to protect against pregnancy and STIs.