How old is a 3-year-old cat in human years?

About 28: 24 for the first two years plus 4 for the third. That's a young adult.

Do cats age faster than dogs?

Early on the pace is similar, but cats usually live longer than most dogs — especially large breeds — so a cat's later years add up more slowly.

When is a cat a senior?

Vets consider cats senior from about 11 years (around 60 in human terms) and geriatric from about 15.

Does indoor vs outdoor change the age?

Not the human-year formula itself, but lifestyle affects lifespan: indoor cats tend to live longer, so they reach these senior ages in better health.

Cat Years to Human Years: How to Calculate Your Cat's Age

Published 6/19/2025 · 3 min read · Everyday calculators

Marco Bianchi — Home, DIY & motoring writer at Allin

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In short

The widely accepted method, backed by the American Animal Hospital Association (AAHA), counts a cat's first year as about 15 human years and the second year as about 9 more — so a 2-year-old cat is roughly 24 in human terms. After that, each additional cat year is worth about 4 human years. A 5-year-old cat is therefore about 24 + (3 × 4) = 36, and a 10-year-old cat about 56. Cats age faster than humans early in life, then settle into a steadier pace.

A cat's first two years equal about 24 human years, then add roughly 4 per year. Learn the AAHA-backed method and see life-stage examples for kittens to seniors.

The two-stage cat aging method

Kittens grow up fast. By their first birthday a cat is roughly equivalent to a 15-year-old human, and by two years old to about 24. That front-loaded first stage reflects rapid physical and sexual maturity. From year three onward, add about 4 human years for every calendar year — a much gentler slope.

Unlike dogs, cats do not vary much by breed or size, so a single schedule works for almost all cats. Our cat age calculator applies exactly this two-stage schedule.

Life-stage examples

A 6-month-old kitten is like a 10-year-old child. At 1 year it's a 15-year-old teenager, at 2 a young adult of 24, at 7 about 44 (middle-aged), and at 15 about 76 — a true senior. Many indoor cats reach 18-20, which is well into their 90s in human terms.

Indoor cats generally live longer than outdoor cats, so a well-cared-for cat can stay in good health long into these senior years. Knowing the human-equivalent age helps you anticipate when to switch to senior food and schedule more frequent check-ups.

What if you don't know the exact age?

For rescued or adopted cats, a vet can estimate age from teeth, eyes and coat. Teeth are the best clue: kittens get adult teeth by about 6 months, tartar builds up after a few years, and worn or missing teeth suggest an older cat. Once you have an estimate, plug it into the calculator.

These figures are estimates. Genetics, diet and whether the cat lives indoors all affect real biological age, so use the result as a helpful guide rather than an exact measurement.

Cat age calculatorConvert your cat's age into human years.Try the tool →

Frequently asked questions

How old is a 3-year-old cat in human years?: About 28: 24 for the first two years plus 4 for the third. That's a young adult.
Do cats age faster than dogs?: Early on the pace is similar, but cats usually live longer than most dogs — especially large breeds — so a cat's later years add up more slowly.
When is a cat a senior?: Vets consider cats senior from about 11 years (around 60 in human terms) and geriatric from about 15.
Does indoor vs outdoor change the age?: Not the human-year formula itself, but lifestyle affects lifespan: indoor cats tend to live longer, so they reach these senior ages in better health.

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