Cat Age Calculator
Enter your cat’s age in years and months to see the rough equivalent in human years. The first year counts as 15, the second adds 9, and every year after that adds 4.
Last updated November 4, 2026
Whole years only; use months for the rest
0 to 11
Result
36 human years
A cat aged 5 years is about 36 in human years (prime adult).
A convention, not a measurement. Breed, lifestyle and health change how a cat ages.
Show the work
Formula: Up to 1 year: 15 x age. Between 1 and 2 years: 15 + 9 x (age - 1). Over 2 years: 24 + 4 x (age - 2).
- Cat age entered: 5 years = 5 + 0 / 12 = 5 years.
- Age is over 2 years: 24 + 4 x (5 - 2) = 36.
Result: 36 human years
How cat years are converted
age 1 = 15
age 2 = 24
after that, add 4 human years for every cat year
A cat reaches the maturity of a teenager within its first year, so the first year counts for 15 human years. The second year adds 9 more, making a 2-year-old cat 24. Every year after that adds 4. A 10-year-old cat is 24 + 8 × 4 = 56.
Ages between whole years are worked out in a straight line. A 6-month-old kitten is 0.5 × 15 = 7.5, and an 18-month-old cat is 15 + 0.5 × 9 = 19.5. Ages up to 30 years are accepted.
See how we calculate for the formulas, sources and review schedule behind every calculator.
A convention, not a measurement
This rule is a widely repeated convention for comparing life stages, not a result measured on individual cats. Breed, indoor or outdoor life, diet and health all change how a cat ages, and different charts give slightly different numbers. Treat the answer as a rough guide.
The calculator also names a rough life stage: under 2 years is kitten or junior, 2 to under 7 prime adult, 7 to under 11 mature adult, 11 to under 15 senior and 15 or more super-senior. These bands are approximate and are not veterinary advice.
How to use the Cat Age Calculator
- Enter your cat’s age in whole years.
- Add any extra months, from 0 to 11.
- Read the age in human years and use Copy, Print or Share to keep it.
Worked example
A cat aged 5 years is 24 for the first two years plus 3 × 4 = 12 more, so 36 human years. A cat aged 2 years and 6 months is 24 + 0.5 × 4 = 26.
| Cat age | Human years |
|---|---|
| 6 months | 7.5 |
| 1 | 15 |
| 2 | 24 |
| 5 | 36 |
| 10 | 56 |
| 15 | 76 |
| 20 | 96 |
Frequently asked questions
How old is a 1-year-old cat in human years?
About 15 by this rule, roughly a teenager. A 2-year-old cat is about 24.
Is one cat year really seven human years?
No. Cats mature quickly in their first two years and then age more slowly, which is why this rule adds 4 human years per cat year afterwards.
Can I enter months?
Yes. Enter whole years and then 0 to 11 months. For example, 1 year and 6 months is 1.5 years, or 19.5 human years.
Is this veterinary advice, and is my data stored?
No. It is a rough guide, so ask your vet about your cat’s care. The calculation runs in your browser and nothing you enter is saved or uploaded.