Pet

Cat Age in Human Years Calculator

Convert a cat's age to a rough human-equivalent age with the common two-year plus four-per-year guide.

Cat age (years)

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The result is the rough human-equivalent age of the cat, so a larger number means an older cat in human terms, and it remains a general guide only.

Formula

The first cat year counts as about 15 human years, the second adds about 9, and each later year adds about 4.

How it works

Early years are weighted heavily because kittens mature quickly, then the yearly addition settles to about four. Indoor and outdoor lifestyles still shift real ageing, so the figure stays rough.

Worked example

For example, a 5-year-old cat gives 15 human years for the first year, plus 9 for the second year, plus 4 for each of the remaining 3 years, which is 15 + 9 + 12 = 36 human-equivalent years.