Calculating Your Cat's Age

Our cats are living longer than ever thanks to better veterinary medicine and an increase of owners keeping them exclusively indoors.

Calculating Cat Age - Older chocolate brown cat and grey kitten with big green eyes on wooden floor

After age two, a cat ages approximately four "cat years" for every calendar year.

It’s not uncommon for cats today to live for 15 or even 20 years! With an increase in older cats, it makes sense that cat lovers would be curious about just how old their cat would be compared to human years. Let’s find out how to calculate a cat’s age.

Calculating your dog’s age in human years is pretty simple, but it depends a lot on size. Unlike dogs, our feline friends are all roughly the same size, so the calculation for your cat’s age is the same no matter what breed of cat you have.

Estimating in Cat Years

Just like dogs, cats age very rapidly during their first two years of life. A cat reaches the approximate human age of 15 during its first year, then 24 at age two. Each year after, it ages approximately four "cat years" for every calendar year. This means that a five-year-old feline would be approximately 36 in cat years. Although there is no concrete scientific way to measure the conversion from cat years to human years, these criteria are generally agreed upon by most cat experts.

According to the Guinness Book of World Records, the world’s oldest cat was Crème Puff, who lived to be 38 years old! That’s the equivalent of 168 years old in human years!

It's worth pointing out that cats who live outdoors age far more quickly, perhaps even twice as fast as an indoor cat. Typically, indoor cats may live 12 to 18 years, with many surviving into their 20s. Outdoor cats face a greater threat of accidents and are more susceptible to illness, and are lucky to live 10 years. Indoor cats stay protected from these threats and typically receive more consistent veterinary care, helping them stay healthier and live longer.

How to Tell a Cat's Age by Examining the Teeth

Calculating Cat Age - Maine coon cat's teeth examined by human hands

Calculating a cat’s age can be done by checking its teeth.

What if you don’t know how old your cat is? How can you tell? Calculating a cat’s age can be done fairly reliably by checking its teeth. Kittens are born with no teeth, but generally have all or most of them by four weeks of age. Just like people, these are baby teeth and will fall out and be replaced. Kittens will have their permanent set of pearly whites by four months old.

From there, it’s a little more of a guessing game. Some cats have worse teeth than others, due to genetics, poor diet, or lack of veterinary care. But for the most part, a young cat under three years will have just a few yellow stains on its mostly-white teeth. If you're seeing tartar on all or most of the teeth, it may be a little bit older, around five years. And if you see heavy yellow or brown staining or even a few missing teeth, you’re probably looking at a senior cat. If you’re not sure, your veterinarian can help you calculate your cat’s age, too.

How old is your cat in cat years?

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