How cat years are counted
The calculator uses the age chart from the 2010 AAFP–AAHA Feline Life Stage Guidelines, written by the American Association of Feline Practitioners and the American Animal Hospital Association and reproduced in the pet age chart hosted by AAHA. Cats do most of their growing up in the first two years, then age at a steady pace.
6 months = 10, 1 year = 15, 2 years = 24
After 2: human age = 24 + 4 × (cat age − 2)
Between the rows the calculator moves in a straight line, so 18 months comes out at 19.5. The chart stops at 21 years (100 human years); past that the calculator keeps adding 4 a year and says so. Under 6 months there is no chart value, so you get the life stage only.
Worked example: an 8-year-old cat
24 + 4 × (8 − 2) = 24 + 24 = 48 human years. The ×7 rule would say 56. Under the 2021 guidelines this cat is a mature adult, and it becomes a senior after its 10th birthday.
Quick reference
| Cat age | Human years | 2021 life stage |
|---|---|---|
| 6 months | 10 | Kitten |
| 1 year | 15 | Young adult |
| 2 years | 24 | Young adult |
| 4 years | 32 | Young adult |
| 7 years | 44 | Mature adult |
| 10 years | 56 | Mature adult |
| 12 years | 64 | Senior |
| 15 years | 76 | Senior |
| 18 years | 88 | Senior |
| 21 years | 100 | Senior |
Life stages in the 2021 guidelines
The 2021 AAHA/AAFP Feline Life Stage Guidelines cut the older six stages down to four, and do not include a human-age table:
- Kitten: birth to 1 year.
- Young adult: 1 to 6 years.
- Mature adult: 7 to 10 years.
- Senior: over 10 years. An end-of-life stage can come at any age.
The human-age number is a talking point; the life stage is what changes the care plan, such as how often your vet suggests checkups and blood work.
Sources checked October 2026.
Questions people ask
How old is a 1-year-old cat in human years?
About 15. Cats grow up fast: by their first birthday they are adult-sized and can have kittens. By 2 they are about 24 in human years, and after that each cat year adds about 4 human years.
Is a cat year seven human years?
No. The ×7 rule badly undercounts young cats (a 1-year-old cat is not like a 7-year-old child) and overcounts old ones. On the vet chart a 15-year-old cat is 76, while ×7 says 105.
At what age is a cat a senior?
The 2021 AAHA/AAFP Feline Life Stage Guidelines call cats over 10 years seniors. The older 2010 guidelines split this into mature (7–10), senior (11–14) and geriatric (15 and up), which is where the numbers on many older charts come from.
Does the chart change for indoor cats or big breeds?
No. Unlike the dog charts, the cat chart is a single table for all cats, because cats vary much less in size than dogs. Diet, weight, genetics and vet care still change how well an individual cat ages, which is why vets go by health and life stage rather than the number alone.
Can I tell my cat’s age if I adopted an adult?
Only roughly. Vets look at the teeth (tartar and wear), eyes, coat and muscle tone. That can usually place a cat as young adult, middle-aged or senior, but not to the exact year. Enter your best estimate; the life stage matters more than the exact number.