Why Do Cats Purr? Here’s What Experts Say

Purring. It’s one of the sweetest sounds to a cat parent’s ears: the subtle, methodical vibration that comes from our cats when we’re playing or relaxing with them.

But what exactly is a purr, and is it always a good thing? We checked in with some experts to find out more about the feline sound we’re all so familiar with.

Purring is caused by the vibration of a cat’s vocal cords.

“What sounds like a sweet symphony to us is actually just a simple flexing of your cat’s larynx and diaphragm muscles as they breathe in and out, which creates a low frequency sound,” explains veterinarian Oscar E. Chavez, BVetMED, MRCVS.

Cat purring is a form of communication, specifically to communicate emotion.

“It’s not all that different than how humans communicate emotions,” Dr. Chavez says.

Those emotions may be positive—a response to “getting scratches, grooming or being groomed, and nursing kittens,” according to veterinarian Sandra Mitchell, DVM, DABVP. Or negative—when they are frightened or stressed.

“What many people don’t realize is that those emotions can vary widely,” says Dr. Chavez. “Cats don’t just purr to communicate that they are content.”

So how do you know what emotion they are trying to communicate? You’ll have to look at other cues, like body language, or even the social setting to better understand the reason why.

This is the reason most cat parents are familiar with. Purring generally occurs when cats are “relaxed and happy,” Dr. Mitchell says.

What are some situations in which a cat would purr because they are content? “Tiny kittens will purr and knead their moms while nursing, which is a sign of contentment,” says Vickie Fisher, former president of The International Cat Association and all-breed judge. In older kittens and cats, contentment purring might occur while they are eating, being pet or lying in a warm, cozy spot, like a heated cat bed.

“They’re purring with a feeling of security of safety,” she notes.

Other ways cats show contentment include kneading a blanket and slow blinking.

“There is some research to suggest that the frequency of the purr has tissue healing properties, so it’s possible that cats purr to self heal, or self soothe,” Dr. Chavez says.

In fact, “as a mom cat goes into labor, they emit huge purrs, thought to actually release a pain management endorphin,” says Fisher.

If your cat is showing other signs of pain, such as limping, not eating or not moving as much, you’ll want to speak with your vet.

When one cat is entering another’s territory, they may purr to signal to the other cat as a friendly gesture that they’re not interested in aggression. “My own cats have a ritual for replacing each other on my lap,” says Fisher.

She continues, “While one cat rests in my lap, purring with contentment at being mom’s sole object of affection, another will hop up next to me and begin purring, while very slowly inching towards the other cat. There will be several minutes of purring and head grooming, and the second cat will carefully lie down as close as possible. Usually, after a bit of time, the first cat will decide things have gotten a bit crowded and will jump off, leaving the second cat to find a more comfortable lap spot. No fighting, no aggression. Just a simple communication of purrs.”

If you have a cat, you’re probably well aware that you almost never need to set an alarm, because your cat is certain to wake you up in the morning by jumping on the bed and purring right in your face. This purring is mostly likely just a way of getting their human’s attention to alert them to the fact that it’s time to be fed.

Other ways they try to get our attention include meowing and licking (you, that is!).

Cats may also purr when they are afraid, as it is thought to “have a calming effect on your cat,” says Fisher. Some situations where they might purr out of fear include visiting the vet or being in a strange environment.

Other signs your cat is fearful or stressed include hiding, loss of appetite and aggressive behavior.

Using your cat’s environment to determine why your cat is purring is the simplest way to determine how they’re feeling.

“It’s never safe to assume that, if a cat is purring, it is happy and content,” says Fisher. “Cat owners should always be vigilant.”

Purring during play, meals and normal routines are usually pretty safely considered “good reasons,” she explains. If the cat is outside their normal environment and purring, it could be that they are trying to self soothe.

Beyond that, Fisher says perhaps the most important purr diagnosis comes when a cat is not feeling well and may require a trip to the vet.

“Obviously, if a cat isn’t eating or is listless and uninterested in normal play behavior, but is purring, there is most likely something wrong,” she says.

An average purr is about 25 decibels, which is on par with whispering, according to the CDC.

The loudest cat purr recorded was from a British kitty named Merlin, whose purr hit nearly 70 decibels and earned him a Guinness World Record. That’s as loud as the noise from a dishwasher or washing machine!

If your cat’s purr sounds more like a pull-start lawnmower revving up than a gentle hum, you don’t need to freak out. As long as your cat is not in immediate physical or mental distress (think: they’re in labor or in a stressful new environment), then you can take a deep breath and enjoy the funny sounds of your four-legged friend.

“Just like some people are louder or quieter than average, so are some cats,” says Dr. Mitchell. “There may be some very loud purrers, even accompanied with drooling in many cases!”

If your cat doesn’t purr, it doesn’t necessarily mean they’re depressed or sick. Dr. Mitchell says that while there are cats that purr frequently and at full volume, “other cats barely purr at all, or don’t purr. Both of these are normal for that individual.”

“Knowing what is normal for your cat and then noticing if anything changes is probably the most important thing for an owner,” she adds.

Translation? If your furry friend is a purring machine one day and then stops suddenly, you may want to pay a visit to your vet to get them checked out to rule out any illness or stress.

Purring is a totally normal behavior for cats—it’s how they communicate their emotions. While it generally means your kitty is feeling happy and cozy, it can also indicate they are stressed or frightened. For that reason, it’s important to pay attention to when exactly your cat is purring and note if their usual behavior changes suddenly.

Jaime Milan contributed to this article.