Cat Age Calculator

Cat years to human years has a cleaner answer than dog years, because two independent sources print the same table. This cat age calculator uses the one in the AAFP-AAHA Feline Life Stage Guidelines, published in 2010 by the American Association of Feline Practitioners and the American Animal Hospital Association in the Journal of the American Animal Hospital Association.

The rule inside the table is short. The first year counts as 15 human years and the second as 9 more, so a 2-year-old cat is 24. Every year after that adds 4: 28 at 3, 32 at 4, 40 at 6, 48 at 8, 56 at 10, 76 at 15 and 96 at 20. The table stops at 25 cat years, which it puts at 116. The cat column of the American Veterinary Medical Association's chart gives exactly the same numbers for ages 1 to 16.

For the default 8-year-old cat that is 24 + 4 x 6 = 48, which the guidelines place in the mature stage.

Kittens are where the table is most detailed and least tidy. It gives a 1-month-old as up to 1 human year, 2 to 3 months as 2 to 4 years, 4 months as 6 to 8, 6 months as 10, 7 months as 12, 12 months as 15 and 18 months as 21. Some of those rows are ranges, and the calculator keeps them as ranges rather than picking a midpoint. Between two rows, a 9-month-old kitten for example, it reads along a straight line from one row to the next: 12 at 7 months, 15 at 12 months, so about 13 at 9 months.

The same guidelines group a cat's life into six stages: kitten from birth to 6 months, junior from 7 months to 2 years, prime from 3 to 6, mature from 7 to 10, senior from 11 to 14 and geriatric from 15 on. The authors write that any such groupings are arbitrary lines along a spectrum, not absolutes. The 2021 update to the guidelines regroups the stages as kitten, young adult, mature adult and senior.

Two cautions. First, the conversion is a way of picturing a cat's age, and the guidelines do not present it as a measurement of how one cat's body has aged. Second, the table runs well past the ages people usually reach: a 20-year-old cat comes out at 96 and the last row, 25, at 116. For what a cat's age means for its care, its own veterinarian is the person to ask.