How the calculator works
Cats grow up fast. By their first birthday most are nearly adult size, so a straight "multiply by seven" rule makes no sense for them. The calculator uses the human-age scale shown in the 2021 AAHA/AAFP Feline Life Stage Guidelines, written by the American Animal Hospital Association and the American Association of Feline Practitioners:
- First year: about 15 human years.
- Second year: about 9 more, so a 2-year-old cat is about 24.
- Every year after that: about 4 more.
For kittens it uses the points that widely shared cat age charts print, about 10 human years at 6 months and 21 at 18 months, and draws a straight line between them, so a 3-month-old kitten comes out at about 5. Months count as a fraction of a year: a cat of 3 years 6 months is 24 + 1.5 × 4 = 30.
To go the other way, switch to Human age → cat years. A 50-year-old person matches a cat of about 8 years 6 months.
These are conventions, not measurements. Cats age at different rates depending on genes, breed, weight, environment and health, so treat the number as a way to picture your cat's stage of life, not as a precise biological age.
Cat age chart: cat years to human years
Human ages are rounded to the nearest year.
| Cat's age | Human age | Life stage |
|---|---|---|
| 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 |
Cat life stages
The 2021 AAHA/AAFP guidelines group cats into four life stages by age:
- Kitten: birth to 1 year.
- Young adult: 1 to 6 years.
- Mature adult: 7 to 10 years.
- Senior: over 10 years.
The same guidelines add an end-of-life stage, which can come at any age. The stages exist to help your veterinarian decide what to check at each visit. A cat does not change overnight on its seventh or eleventh birthday. The calculator keeps a cat in the young adult stage until its 7th birthday and calls it a senior once it is past 10.
Example: a cat of 4 years 8 months
- 4 years 8 months is 4.67 years.
- The first two years count as 24 human years.
- The remaining 2.67 years × 4 = 10.7 human years.
- 24 + 10.7 = 34.7, so the cat is about 35 in human years.
That makes it a young adult. It moves into the mature adult stage at 7, when it will be about 44 in human years.
Tips for using cat years
- Use it as a conversation starter, not a diagnosis. Two 12-year-old cats can be in very different shape. Your veterinarian's exam tells you far more than any age chart.
- Watch for changes rather than birthdays. A change in appetite, thirst, weight, grooming or litter box habits is worth a vet visit at any age, and especially in a mature or senior cat.
- Rescue cat with no birthday? Pick the middle of the age range your vet estimates and enter that. You can always adjust it later.
- Indoor and outdoor cats use the same chart. Lifestyle affects health and lifespan, but the convention for converting ages does not change.
Frequently asked questions
How old is my cat in human years?
A 1-year-old cat is roughly 15 in human years and a 2-year-old about 24. After that, add about 4 human years for every cat year, so a 5-year-old cat is about 36, a 10-year-old about 56 and a 15-year-old about 76.
Is one cat year equal to seven human years?
No. Cats grow up much faster than that at the start. A 1-year-old cat is close to adult size and can have kittens, which the times-seven rule would call a 7-year-old child. After the second birthday cats age more slowly, about 4 human years per year.
At what age is a cat considered a senior?
The 2021 AAHA/AAFP Feline Life Stage Guidelines call cats over 10 years old seniors. Cats from 7 to 10 are mature adults. The stages help your veterinarian plan checkups and screening; they are not a sign that anything is wrong.
When does a kitten become an adult cat?
The AAHA/AAFP guidelines treat cats as young adults from their first birthday. Most cats are close to full size by then, although some large breeds, such as Maine Coons, keep filling out for longer.
How can I tell how old my cat is if I don't know its birthday?
Ask your veterinarian. Teeth are the best clue in young cats, because kittens have all their adult teeth by about six months. In adults, tartar, tooth wear, eyes, coat and muscle tone give a rough range rather than an exact age.
Last updated October 17, 2026.