What are testicles? What do they actually do apart from hang there? Read on...

Testicles need to be 1-2 degrees cooler than body temperature

What are they?

Balls, nads, nuts, jewels, bollocks... whatever you may call them, males have two testicles inside the scrotum. They have two jobs:

  • To make sperm. Up to 150 million per day. Enough to father a country the size of Russia. Respect.
  • To make testosterone. This is the male hormone which makes men grow stronger. It makes the pubes and penis grow and the voice deepen.

So why store such vital bits of equipment in a flimsy skin sack, ready to get kneed? Testicles need to be 1-2 degrees cooler than body temperature to work properly. In fact, they shrink when warmed up (don't try this at home).

Testicles start growing around 11-12 years old. This is usually the first sign of puberty.


There is less variation in testicle size than in penis size. But bigger balls do not mean a bigger dick (or better man).

In healthy European adult humans, the average size for each testicle is 18cm³, with normal size ranging from 12 cm³ to 30 cm³.

Both testicles should be about the same size and shape. It is common for one (often the left) to hang slightly lower than the other. It stops them knocking each other when you move.

Examining your testicles

You should take a closer look at your balls regularly, to check everything's in working order. Here's three reasons why it's important:

  1. In 2012 3,286 men in the UK were diagnosed with testicular cancer.
  2. Testicular cancer is the most common cancer of men aged 15-49 in the UK.
  3. Cases of testicular cancer has more than doubled in Britain since the mid 1970s. However, most cases can be treated successfully.

What to do

  • Stand up and take each ball in turn in both hands
  • Feel gently around each ball
  • They should feel smooth, firm and oval-shaped

If you notice any lumps or swelling, head to your GP to get them checked. Most lumps in the testicles are harmless.

BBC Advice factfiles are here to help young people with a broad range of issues. They're based on advice from medical professionals, government bodies, charities and other relevant groups. Follow the links for more advice from these organisations.


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