Cat Age Calculator
Convert cat years to human years and find your cat's life stage.
Your cat
Indoor cats commonly reach 15–20 years; outdoor cats average far fewer, largely from traffic, predators and infectious disease. Twice-yearly check-ups are usually advised from around 11, when kidney disease, hyperthyroidism and arthritis start showing up.
This converts your cat's age into human years and tells you which life stage they are in: kitten, young adult, mature, senior or geriatric.
It also shows roughly how far through a typical lifespan your cat is, which is often the more useful answer if you are trying to judge what care they need next.
How old is a cat in human years?
Cats age quickly at first and then settle down. The first year is worth about 15 human years, the second adds around 9 more, and every year after that counts as roughly 4.
So a two-year-old cat is about 24 in human terms: fully grown, independent, and at the peak of its physical condition. That is why kitten food and kitten vaccination schedules stop around then.
Unlike dogs, size makes almost no difference. A Maine Coon and a Siamese age at much the same rate, so there is no weight input here. What does change things is whether a cat lives indoors or out.
A 10-year-old cat works out at 24 + (8 × 4) = 56 human years. The old multiply-by-seven rule would say 70, which overstates it considerably.
What to enter
- Age in years
- Your cat's actual age. For a rescue with no known birthday, a vet can estimate from teeth and eye condition.
- Plus months
- Worth filling in for kittens, where a few months is a large share of their life so far.
The five life stages, and what changes at each
- Kitten (0–1)
- Rapid growth, vaccinations, neutering. Ends around the first birthday.
- Young adult (1–7)
- Physical prime. Annual check-ups, weight watching as activity drops after neutering.
- Mature adult (7–11)
- Roughly human middle age. Weight gain and early kidney or dental problems tend to start here.
- Senior (11–15)
- Many vets move to twice-yearly check-ups and routine blood tests.
- Geriatric (15+)
- About 76 human years and up. Comfort, mobility and appetite become the things to watch.
What this assumes
The cat is reasonably healthy. Chronic illness and obesity both shorten lifespan noticeably.
Life stages follow the AAHA and AAFP framework, which is what most vets use.
How to calculate your cat's age in human years
Three steps, and the arithmetic is easy enough to do while the cat sits on the keyboard.
- 24
- The first two years: 15 then 9
- × 4
- Every year after the second
First year is 15. A one-year-old cat is roughly a 15-year-old human: fully grown and able to breed.
Second year adds 9. So a two-year-old cat is about 24.
Then 4 a year. No size adjustment needed, unlike dogs.
See a worked example: a 15-year-old cat
- Age
- 15 years
First two years give 24.
That leaves 13 more years.
13 × 4 = 52.
24 + 52 = 76 human years, which puts the cat firmly in the geriatric stage.
About 76 human years
Frequently asked questions
No. That rule has no scientific basis and understates the first two years badly while overstating everything after.
A one-year-old cat is not a 7-year-old child. It is fully grown, sexually mature and able to have kittens of its own, which is much closer to 15.
About 56 in human years: 24 for the first two years, then 8 more years at roughly 4 each.
That places them in the mature adult stage, moving towards senior. It is the point where many vets start recommending routine blood work to catch kidney changes early.
Considerably, and it is the single biggest factor in cat lifespan. Indoor cats commonly reach 15 or more, while cats with unsupervised outdoor access often average far less.
The causes are traffic, fights and the infections they spread, predators and poisons, none of which are about ageing itself.
Far less than it does in dogs. A large Maine Coon and a small Siamese age at broadly similar rates, which is why there is no size input on this page.
Some pedigree breeds do carry inherited conditions that affect lifespan, but that is a health risk rather than a different ageing speed.
Around 11 years, with 15 and over usually classed as geriatric. The stage before that, mature adult, starts at about 7.
The practical change is check-up frequency: twice yearly rather than annually, since six months is a meaningful stretch of a senior cat's life.
Problems people actually run into
Missing the mature stage because the cat seems fine
Cats hide illness extremely well, and a 7 to 11 year old cat usually looks and behaves exactly as it always has.
That is the window where kidney disease, dental problems and thyroid changes typically begin, and all of them are far more manageable when caught early. A cat that seems perfectly healthy at 9 is precisely the one worth screening.
Results are estimates for general information only and are not professional financial, medical, or legal advice. Read our full disclaimer.
Sources
- AAFP/AAHA Feline Life Stage Guidelines · American Association of Feline Practitioners
Last updated: September 3, 2026