Why Do Cats Purr? The Reasons Behind It

There's more behind the cat noise than you realized.

When a purring cat rubs against you, you can’t help but feel pleased with yourself. That cute little kitty must just love you, right? But you may not want to move on from petting that cat to patting yourself on the back just yet. Happiness isn’t the only thing that makes cats purr.

How do cats purr?

Cat owners may find themselves wondering, not only why do cats purr, but how do they do it? How do they create that distinctive noise? Well, contrary to what you might think, cats don’t have a unique body part or vocal organ that allows them to purr. Instead, the sound comes from rapid movements in their voice box. “A purr starts as a signal from the central nervous system that travels to muscles in the voice box,” explains Daniel Rotman, Founder & CEO of PrettyLitter. “These muscles tighten and release very quickly while the cat inhales and exhales to make the vibrations that we can feel and hear.” If you’re curious about other kitten stereotypes, find out if your cat should be drinking milk.

So why do cats purr, anyway?

Well, because it’s what they’re born to do. Cats start purring, and hearing purring, from infancy. Mother cats purr to lead their kittens—which are blind and deaf when they’re born—to them for food and warmth. In turn, vets believe, kittens purr to show they’re OK and help them bond with mama cat. “As cats grow older, purrs are used [for] anything from communicating joy and contentment to soothing pain,” Rotman explains. Don’t miss these 17 other things your cat would love you to know.

What does it mean when a cat purrs?

So what makes a cat purr? Sure, you might hear purrs when your pet feels relaxed or friendly, but cats also purr when they’re hungry, stressed, or in pain. “All behavior depends on history, context, and expectation,” Tony Buffington, a cat expert and veterinarian at Ohio State University, told Wired. “So it’s naive to think that cats can only purr for one reason—it’s like thinking that people can only laugh for one reason.” Like how some guffaws are a reaction to humorous cat memes while other giggles could come from nerves, cats’ purrs are open to interpretation. Beware of the subtle signs your cat could actually be depressed, or even just cranky. 

Purrs release feel-good endorphins, so experts think cats use the vibrations to soothe themselves. That could mean your cat purring while enjoying some cozy cuddles from you, or it might help calm their nerves—or literally heal their pain. Mother cats have been known to purr while giving birth. Also, studies have found that whole-body vibrations of 35 to 50 Hz could help stimulate bone healing. Cats’ purr frequencies range from 25 to 150 Hz, and some suggest the vibrations could help kitties keep their skeletons strong. (Sounds crazy, but even NASA astronauts have used vibration therapy in space, where lack of gravity means no bone-healthy weight-bearing exercise.) You may not be able to train your cat to purr on command, but you can train your cat to do other things.

As for purr frequencies even higher than 150 Hz, those serve an entirely different purpose. One study in the journal Current Biology found that when cats were trying to get their owners to feed them, their purr frequency shot up to 220 to 520 Hz—awfully close to the 300 to 600 Hz of a human infant’s cry. Researchers suggest the higher frequency makes the sound harder for cat (and baby) parents to ignore. Bottom line: Not all purrs are created equal. Having a cat can be beneficial for your health, but you should think twice before sleeping with your cat.

How can you determine why your cat is purring?

Though purring isn’t only a sign of contentment, you shouldn’t launch into panic mode the next time you hear the noise. There’s a reason people associate it with happiness—it is still the primary reason you’ll find your cat purring. “They may purr when they have been injured or are in pain, but among our furry companions it is more often a sign of contentment,” Rotman explains.  By the way, have you ever wondered why cats are afraid of cucumbers?

The best way to figure out your cat’s message is by looking at what else is going on. If it’s dinnertime, or if the frequency of the purring is a little higher, your furry friend might have food on the brain. If your kitty nips at you or swipes with her paws, she’s probably annoyed or mad—even if she’s purring. Also be listening for continuous, insistent vocalizing from your cat, whether that’s purring or, more commonly, meowing (or both). If the vocalizing goes on for 24 to 36 hours, this could be one of the signs your “healthy” cat is actually sick. But a cat purring away while curled up on your lap is probably just enjoying your company. Next, learn the mistakes cat owners should never make.

Marissa Laliberte
Marissa Laliberte-Simonian is a London-based associate editor with the global promotions team at WebMD’s Medscape.com and was previously a staff writer for Reader's Digest. Her work has also appeared in Business Insider, Parents magazine, CreakyJoints, and the Baltimore Sun. You can find her on Instagram @marissasimonian.