Cat age in human years
Convert a cat's age to human years and see its life stage, with what each stage usually needs.
Runs in your browser: nothing you enter is sent to this site. Results are planning figures, not veterinary advice. For a medical decision, ask your vet.
What it is
A calculator that turns a cat's age into a rough human equivalent and names the life stage. It uses the common rule of thumb: the first year of a cat's life counts as 15 human years, the second as 9 more (24 in all), and each year after that as 4.
How to use it
- Enter the cat's age in years and extra months.
- Read the human-year equivalent and the life stage. The table below the result shows the same conversion for other ages.
- If your cat's age is a guess, as with a rescue, ask a vet. Teeth and eyes give a fair estimate.
How it works
The conversion is a simple formula: up to one year, 15 times the age; from one to two years, 15 plus 9 for each year past the first; after two years, 24 plus 4 for each year past the second. A 10-year-old cat comes out at 56, and a 15-year-old at 76.
The life stages follow the groupings veterinarians use: kitten up to one year, young adult from one to six years, mature adult from seven to ten, and senior beyond ten.
What it cannot do
Cats age at different rates, by breed, by weight and by how healthy they have been. Indoor cats tend to live longer than outdoor cats. Treat the human age as a way to picture a stage of life, not as a medical measure.
An older cat's behaviour changes can be signs of illness. Changes in drinking, weight, appetite or litter-box habits are worth a call to your vet at any age.
Last reviewed November 7, 2026