Cats grow up fast. A one-year-old cat is fully grown and can have kittens, much like a human teenager of 15. At two it is a young adult of 24. From then on, each cat year counts about four human years. The calculator applies that curve to the age you enter, in years and months, and adds the life stage the feline vets’ guidelines use.
Example: a cat that is 6 years and 6 months old. 24 for the first two years, plus 4.5 × 4 = 18: 42 human years, a young adult by the guidelines. Six months later it becomes a mature adult.
Cat years to human years
| Cat’s age | Human years | Life stage |
|---|---|---|
| 6 months | 8 | Kitten |
| 1 | 15 | Young adult |
| 2 | 24 | Young adult |
| 3 | 28 | Young adult |
| 4 | 32 | Young adult |
| 5 | 36 | Young adult |
| 6 | 40 | Young adult |
| 7 | 44 | Mature adult |
| 8 | 48 | Mature adult |
| 9 | 52 | Mature adult |
| 10 | 56 | Mature adult |
| 11 | 60 | Senior |
| 12 | 64 | Senior |
| 13 | 68 | Senior |
| 14 | 72 | Senior |
| 15 | 76 | Senior |
| 16 | 80 | Senior |
| 17 | 84 | Senior |
| 18 | 88 | Senior |
| 19 | 92 | Senior |
| 20 | 96 | Senior |
The four life stages
The 2021 AAHA/AAFP Feline Life Stage Guidelines replaced six stages with four, plus end of life:
- Kitten (birth to 1 year): vaccinations, neutering, socialization; the most growth and the most food per kilogram.
- Young adult (1–6 years): a check-up at least once a year; watch the weight, since many cats put it on after neutering.
- Mature adult (7–10 years): still a yearly visit, now with more attention to teeth, weight and the first signs of disease.
- Senior (over 10 years): a check-up every six months, with blood and urine tests and blood pressure. Kidney disease, an overactive thyroid and arthritis become common, and cats hide pain well.
The guidelines add that the stages are not rigid: a fit 12-year-old can be treated like a mature adult, at the vet’s discretion.
Why “× 7” fails for cats
Multiplying by seven makes a one-year-old cat 7 – a child – when it is in fact grown up, and makes a 20-year-old cat 140. The 15-24-plus-4 curve fits much better at both ends. Like every such rule it is an average: genes, diet, weight and whether a cat lives indoors all shift the real picture. For the dog version, with size differences, see the dog age calculator.
Once zet4u is saved on your phone, the calculator works offline, in a waiting room with no reception too.
Frequently asked questions
How old is a 10-year-old cat in human years?
About 56. The first year counts 15 human years, the second brings the cat to 24, and each year after adds about 4: 24 + 8 × 4 = 56.
At what age is a cat a senior?
Over 10 years, according to the 2021 AAHA/AAFP Feline Life Stage Guidelines. Before that come kitten (to 1 year), young adult (1–6) and mature adult (7–10). The guidelines recommend a check-up at least once a year, and every six months for seniors.
Do indoor cats age differently?
The conversion is the same: it describes how a cat's body matures and ages, not how long a particular cat will live. Indoor cats avoid traffic, fights and many infections, which is one reason vets recommend keeping cats indoors or in a safe outdoor space.
How old is the oldest cat?
Guinness World Records lists Creme Puff, a cat from Austin, Texas, who lived to 38 years and 3 days (1967–2005). By this calculator, that is about 168 human years – a reminder that the conversion is an average, not a law.
Sources
- AAHA/AAFP: 2021 Feline Life Stage Guidelines
- American Association of Feline Practitioners: life stage resources
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