How old is a 21-year-old cat in human years?

A 21-year-old cat is about 100 in human years on International Cat Care’s chart. Its life stage is super senior.

Patient recordCat
Age
21 years
Stage span
15+ years

Human age

100years

International Cat Care chart

Vet guideline stageAAHA/AAFPSenior
“Times 7” rulewhy it’s wrong147

First two years count as 24 human years, then 4 for every year after.

Life stage (International Cat Care)

  • Kitten
  • Junior
  • Adult
  • Mature
  • Senior
  • Super senior (this stage)

AVMA calls cats senior after about 10 years. The AAHA/AAFP guidelines add that some healthy older cats are best treated as mature adults.

For years and months, use the cat age calculator.

The math

24 + 4 × (21 − 2) = 24 + 76 = 10024 for the first two years, then 4 for each of the next 19.

Times 7 would say 147, which is 47 years too high next to the chart.

Life stage at 21 years

International Cat Care: Super senior (15+ years). 2021 AAHA/AAFP guidelines: senior. International Cat Care says many cats reach this stage, and that close attention to small changes in behavior matters most now.

Nearby ages

Cat ageHuman yearsLife stageTimes 7
18 years88Super senior126
19 years92Super senior133
20 years96Super senior140
21 years100Super senior147
22 years104Super senior154
23 years108Super senior161
24 years112Super senior168

See all ages in the cat years chart.

Sources

  1. International Cat Care, “How to tell your cat’s age in human years.” The cat age chart (to 25 years) and its six life stages.
  2. 2021 AAHA/AAFP Feline Life Stage Guidelines. Kitten up to 1 year, young adult 1 to 6, mature adult 7 to 10, senior over 10.
  3. AVMA, “Pets age faster than people” (PDF). Dog column for a medium-size dog of 21 to 50 lb, ages 1 to 16; cat column, ages 1 to 16. AVMA adds that pet ages are approximate and that weight and breed may influence aging.
  4. AVMA, “Caring for senior cats and dogs.” Dog size groups by weight, the age each group becomes senior, cats senior after about 10, and the statement that dogs don’t age 7 human years per year.