Reviewed and updated for accuracy on November 18, 2019, by Dr. Hanie Elfenbein, DVM, PhD
When you adopt a cat whose history is a mystery to the shelter or rescue organization, it’s hard to determine how old your new feline friend may be.
Once your kitty reaches adulthood, pinpointing a birthday becomes increasingly difficult. However, there are some indicators that can help you and your vet make an educated guess.
Dr. Michael Nappier, an assistant professor of community practice at the Virginia-Maryland College of Veterinary Medicine’s Department of Small Animal Clinical Sciences, says that these indicators are far from precise, “but they are more able to give owners and vets a general idea.”
Here are six tips that you and your vet can use to tell a cat’s age.
The younger the cat, the easier it is for vets to determine about when they were born.
“Factors such as the cat’s size and teeth can be very useful in pinpointing an age,” says Dr. Stephen Horvath, clinical assistant professor at the College of Veterinary Medicine at Ohio State University.
“Up until cats are about 4 to 6 months old, a good rule of thumb is that they gain a pound for every month,” Dr. Horvath explains. “So a 3-pound kitten is 3-months old, a 4-pound kitten is 4 months, and so on until about 6 months of age.”
However, Dr. Nappier says that this method isn’t foolproof. “If the cat is in poor health, weight is no longer a reliable age indicator.”
The other age indicator that can be used for kittens is their teeth.
A kitten’s deciduous (baby) teeth start to come in when they’re about 2 weeks old, and finish when they’re about 8 weeks old.
Then, at around 4 months old, the baby teeth start to fall out, and adult teeth start to erupt. A cat should have all of their adult teeth by the time they’re 7 months old.
“Once that happens, it’s really hard to tell how old a cat is by its teeth,” Dr. Horvath says.
Dr. Horvath notes that while it becomes more difficult to estimate a cat’s age by their teeth once all the adult teeth are fully erupted, it’s not impossible.
“We can also use the wear and tear as well as tartar buildup as clues to a cat’s age,” he says. “Typically, if we see just a little bit of tartar, especially along the cat’s cheek teeth (the teeth that run along the sides of the cat’s mouth), that cat is 1 to 2 years old. The more tartar that accumulates, the older the cat probably is.”
However, like people, some cats just have worse teeth than others. A young cat could exhibit lots of tartar, and an older one could have very little. Therefore, using tartar as the lone indicator of age is a lot less exact than many owners might hope.
Gingivitis (inflammation of the gums) is also not a reliable indicator of age. Some cats develop severe gingivitis at a very young age, while others don’t develop the disease until tartar accumulates on the teeth.
Beyond teeth, vets may also look to your cat’s eyes to help determine age.
Around the age of 6 or 7, a cat’s eye lenses become denser, not unlike what happens to humans around age 40. “If you look with an ophthalmoscope, you can see a bit of cloudiness around this age,” Dr. Horvath explains.
It’s not really noticeable to owners until a cat is about 10 years old—then their eyes might start to look a little cloudy.
Dr. Nappier adds that looking at the cloudiness in the eye is something that vets must do, especially when the cat is younger. “It’s a fairly reliable system with a set of standards, but it’s not something owners can do at home without having certain tools and knowledge,” he says.
As cats age into their senior years, their iris (the colored part of the eye) can show changes. Called iris atrophy, the inside of the iris can break down so that your cat’s pupil doesn't get as small as it used to. Or, sometimes the inner edge of the iris becomes wavy.
Either way, this is a normal aging change and does not cause any pain or problems for your cat.
Cats are very meticulous when it comes to grooming, and most younger cats will keep their coats looking pristine. However, once cats reach a certain age, they might not be as thorough with their grooming as they once were.
“Many factors can contribute to a cat losing the ability to groom themselves well. Dental issues in particular can cause a cat to stop grooming because it is painful. They also could gain weight as they get older, which in turn makes it harder to reach certain spots,” Dr. Horvath says.
Arthritis can be another factor since the contortions necessary to reach everywhere on the body become painful. “Losing the ability to groom is more obvious in medium-haired and long-haired cats,” adds Dr. Horvath.
Most cats who live long enough will eventually experience changes in their anatomy and physiology that can be picked up by veterinarians.
For example, certain diseases, like kidney disease or an overactive thyroid, are quite common in older cats but relatively rare in the young. Dr. Horvath says that older cats often become “unable to process proteins as easily, so they lose a lot of the protein they eat and start to lose weight.”
With a thorough examination, your veterinarian can get a better picture of your cat’s age.
Dr. Horvath and Dr. Nappier repeatedly emphasize that determining the age of a cat without knowing its history is truly a guessing game.
“We can look at the cat’s eyes and teeth, do blood work and see how different organs are functioning, listen to the heart, and even measure muscle and fat, but unfortunately there isn’t one specific attribute that allows us to say definitively that a cat is a certain age,” Dr. Horvath says. “It’s really just making an educated guess.”
But no matter your cat’s age, there are many ways you can help keep your cat healthy—encouraging exercise through play, providing a healthy diet and taking your cat for regular veterinary visits.
By Kate Hughes