How cat years are calculated
The standard veterinary scale counts a cat's first year as about 15 human years, the second year as another 9 (so a 2-year-old cat ≈ 24), and every year after as 4 more. A 5-year-old cat therefore equals 24 + (5−2)×4 = 36 human years.
Working through a few ages: a 6-month-old kitten is around 10 human years, a 3-year-old cat is 28, a 10-year-old cat is 56, and a 15-year-old cat is about 76. Cats are generally treated as senior from around 11 years.
The age calculator is the natural next step once you have this figure.
Why kittens age so fast
Cats reach sexual maturity and near-adult size within their first year, which is why the early years count for so much. The pace then settles to a steady four human years per cat year. Have a dog too? Compare with the dog age calculator.
Breed makes a modest difference. Siamese and other Oriental breeds often stay lively well into their teens, while large breeds such as Maine Coons mature slowly and may not reach full size until three or four years old. Body condition, dental health and whether the cat is neutered shape real ageing far more than the arithmetic does.
The dog pregnancy calculator answers the question that usually follows this one.
How to use this calculator
Enter your cat's age in years — decimals are fine for kittens — and the human-equivalent age appears instantly. Planning a litter? See the cat pregnancy calculator.
If you adopted an adult cat with no known birthday, a vet can estimate age from teeth, coat and eye clarity, and you can enter that estimate here.
Frequently asked questions
- How old is a 5-year-old cat in human years?
- About 36 human years: 24 for the first two years plus 4 for each of the next three years.
- How old is a 1-year-old cat?
- Roughly 15 human years — a 1-year-old cat is already a young adult.
- Do indoor and outdoor cats age differently?
- The scale is the same, but indoor cats often live longer overall thanks to fewer hazards.
- Is this scale exact?
- It is a widely used approximation. Individual cats vary with breed, health and lifestyle.
- When is a cat considered senior?
- Most vets treat cats as senior from about 11 years, roughly 60 in human terms. Twice-yearly check-ups are commonly suggested from that point, so ask your vet what fits your cat.