Calculators
Cat Age Calculator
Convert a cat age in years and months to human years with a life stage locally in your browser.
Enter your cat's age in years and extra months. Uses first year = 15 human years, second year = +9 (24 total), each year after that = +4. The calculation runs locally in your browser; your values are not uploaded or stored.
Find a cat age in human years without uploading anything.
Enter your cat's age in years and extra months to see the human-age equivalent and life stage with the formula shown. Everything runs locally in your browser, so your values are not uploaded or stored.
Frequently Asked Questions
Everything you need to know about this tool, how it works, and privacy.
What does the cat age calculator show?
Enter your cat's age in years from 0 to 30 plus optional extra months from 0 to 11. The calculator returns the human-age equivalent and the life stage from kitten to geriatric with the calculation shown. For example, a 4-year-old cat maps to about 32 human years and the Prime stage.
Which formula does the cat age calculator use?
It uses the common veterinary rule of thumb: the first year equals 15 human years, the second year adds 9 (24 total), and each year after that adds 4. Ages under one year scale linearly within the first year, so a 6-month-old kitten maps to about 7.5 human years. Real ageing varies by breed, size, and health, so treat the result as an estimate.
Which inputs are accepted?
Enter whole-number cat years from 0 to 30 and whole-number extra months from 0 to 11; the months field may be left blank for 0. The total age must be greater than zero and no more than 30 years. Kittens under one month can be entered as 0 years and 1 month. Missing years, fractional values, non-numeric text, and values outside these ranges show a clear error instead of a result.
Do my values stay private?
Yes. The calculation and copy action run locally in your browser. CodeASystem does not upload or store the values you enter.