How to convert cat years to human years
Enter your cat’s age in completed years. This calculator uses the familiar comparison of 15 human years at a cat’s first birthday, 24 at the second, then four additional human years for each additional cat year. The result is an analogy that makes age easier to discuss. It is not a measurement of health, biological aging or life expectancy.
Use the age your cat has already reached: a cat aged five years and eight months is entered as five. This whole-year tool deliberately avoids assigning a precise human-age number to each month. If your cat’s birthday is uncertain, the result is only as approximate as the age you enter.
The cat-age formula and a worked example
At one year, the comparison is 15. At two years or older, use 24 + 4 × (cat age − 2). For a five-year-old cat, 24 + 4 × 3 = 36 human years. At ten years, the same rule gives 56.
Multiplying every cat year by seven gives a different result because it treats early development and later adulthood as identical. This staged convention uses a different comparison for the first two years. Neither approach can tell you how healthy an individual cat is.
Cat years to human years chart
The values below use the same formula as the calculator. The chart covers completed ages 1–20; the tool also accepts ages through 25.
| Cat years | Human years | 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 |
Feline life stages are a separate guide
The 2021 AAHA/AAFP guidelines group cats into kittens under one year, young adults aged 1–6, mature adults aged 7–10 and seniors over 10. The calculator applies these age bands to completed years. It does not calculate a life stage from the human-year number.
These categories can help organize a conversation with your veterinarian. They are not a diagnosis, and a birthday does not cause an abrupt change in health. Ask your veterinary team what care is appropriate for your cat’s history and current condition.
Frequently asked questions
Do indoor and outdoor cats use different conversions?
This tool uses the same age comparison for both. It does not have a validated numerical adjustment for lifestyle, breed, size or medical history, so it does not invent one.
How old is a 15-year-old cat in human years?
The conventional comparison is 76: 24 + 4 × 13. A 15-year-old cat is in the senior feline life-stage group, but the number does not predict remaining lifespan.
Why can’t I enter a kitten’s age in months?
The early months involve rapid development. This calculator is limited to the whole-year convention rather than interpolating a precise monthly number. A veterinarian can discuss a kitten’s development and age estimate.
Can I use the dog calculator for my cat?
No. The dog age calculator uses a different model. Use species-specific context, and treat both outputs as estimates rather than medical assessments.
Sources and method limits
The age comparison follows the whole-year values in the Feline Veterinary Medical Association age chart. Life-stage labels use the whole-year bands in the 2021 AAHA/AAFP feline life-stage definitions: ages 7–10 are mature adult, with senior beginning after 10. Sources checked October 3, 2026. No individual veterinary assessment is implied.