Why do cats purr?

KohakuA cat's purr is so soothing to hear, isn't it? But is it always a sign of contentment?

The answer in 30 seconds

In fact, the reason is still not fully understood.

The reason cats purr is not fully understood. Cats often purr when they are content, but they also purr when they are hurt or in pain. Research has also found that when cats beg for food, a high-pitched sound like a baby's cry is sometimes mixed in.

A brown tabby kitten lying down and relaxing on a sofa — A cat relaxing on a sofa. Cats often purr when they are content.Photo: Erik-Jan Leusink ejleusink / CC0 / Wikimedia Commons

The reason is not fully known

According to the U.S. Library of Congress, the reason cats purr is not fully understood. Purring is often taken as a sign of contentment, but cats are also known to purr when they are hurt and in pain. A purring cat is not always a happy cat.

Figure: When cats purr

A signal between kittens and mother

Kittens start purring within a few days of birth, and they purr while nursing. Veterinarians think this is a signal that tells the mother cat "I'm fine" and "I'm here," and that it also plays a part in the bond between mother and kittens.

Purring to beg

A study at a university in the United Kingdom found that when cats purr to beg for food, a high-pitched sound like a baby's cry is mixed in. People who heard this sound felt it was "urgent" and "not very pleasant," even if they had never owned a cat. Cats may be cleverly using a sound that makes people want to take care of them.

KohakuThere is even a special purr for begging. Cats are quite good at asking, aren't they?

How do cats make the sound?

A purr keeps going whether the cat is breathing in or out, and the larynx (the organ that makes the voice), deep in the throat, is involved. A 2023 study found that simply sending air through the larynx produced vibrations of about 25–30 times a second, and suggested that soft "pads" on the vocal folds may help make the low sound. There is also an idea that low vibrations help injuries heal, but it has not been confirmed.

Figure: How the purring sound is made

Want to know more?

Bobcats, cheetahs, and pumas also purr, but lions, tigers, and similar big cats are said not to purr in the true sense.
Cats whose larynx muscles become paralyzed and stop moving are known to lose the ability to purr.
A cat's purr is a very low sound of about 20–30 hertz, a pitch usually made by large animals such as elephants.

KohakuCats purr not only when content but in many different situations. Research into why is still going on.

Quick quiz: test yourself

When do cats purr?

Show the answer

Only when they are content
Only when they are sleepy
Also when hurt or in pain

Also when hurt or in pain Cats often purr when content, but also when hurt or in pain, and when asking for food. The exact reason is not yet clear.

Sources

Why and how do cats purr?Library of Congress
The cry embedded within the purrCurrent Biology
How do cats purr? New finding challenges long-held assumptionsScience（AAAS）

This article was written after checking the sources above as of 2026-10-03. Explanations may change as research progresses. Photo credits are shown below each photo.