Cat Years To Human Years: How Old Is My Cat?

By Helen Anne Travis

When you adopt a cat from a shelter or take in a stray, it’s usually impossible to know the exact age of your newest family member. Sure, there’s a clear difference between a kitten and a senior cat-izen but to the untrained eye, the years in between might look a lot alike. You’ll likely bring her to a veterinarian, who will conduct a physical exam and maybe run some tests to help determine your kitty’s approximate age. But what exactly do doctors look at? And how precise are their estimates?

To learn more, we caught up with Dr. Erick Mears, the medical director for BluePearl Veterinary Partners in Florida, and Dr. Rachel Barrack of Animal Acupuncture in New York City to find out how the experts determine a cat’s age.

 

How Old is My Cat? A Vet’s Perspective

Because every animal matures at a different rate, even veterinarians have trouble knowing for certain how many years, months and days a cat has been on the planet. They can, however, make a very educated guess.

“When I’m giving someone an estimate on their cat’s age, I tend to start by looking at the teeth,” Barrack said. Teeth can be strong indicators of a cat’s potential age, especially in younger animals. A kitten’s baby teeth will usually start to come in when they around three weeks old, with all 26 being present by the time they are around six weeks old. Ages between three to six months can be determined by the rate at which the baby teeth are falling out and their permanent replacements are coming in.

If veterinarians see a full set of adult teeth, they usually assume the cat is at least six months old, and if those teeth are clean and sharp, the cat is likely younger than two. After that, however, things can get murky. “Beyond age two it becomes a lot harder to tell the cat’s age by its teeth,” Mears said.

After looking at a cat’s teeth, doctors then examine the coat and muscular system for more clues. Younger cats typically have shiny coats and strong muscle definition in their legs and along their backs. Around age 10 to 14, cats can start having problems digesting protein and fat and may have a reduced muscle mass and lose weight as a result. Older cats are also at high risk for developing arthritis that limits their mobility and ability to groom themselves, resulting in a coat that becomes dull and matted.

Beyond the physical exam, lab work on older kitties can help veterinarians pinpoint a patient’s age. Kidney issues may show up around age ten, and hyperthyroid indicators a year or two later, however Mears said that he has seen these in cats as young as six or as old as 22.

So How Long is a Cat Year in Human Years?

Once you know roughly how old your kitty is, you can compare her age to your own. It turns out that the ratio of cat years to human years isn't as simple as a single conversion rate; cats develop the fastest during their first two years of life and then slow down. So at the end of her first year, your cat is approximately at the same developmental stage as a human that is 10 or 15 years old, and by age two, your cat will be around 25 in human years. “After that, cats tend to develop more slowly,” Barrack said, aging about four or five human years every 12 months.

Putting your pet’s age in human terms not only helps you empathize with your cat, it also show the importance of regular veterinary checkups. “A year time frame in a cat’s life is significant,” Mears says. “Things can change dramatically.” If an adult cat year is equivalent to four or five human years, it’s easy to see how arthritis could develop, organ function could decrease and neurologic changes might develop is such a seemingly short period of time. 

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