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How to Calculate Cat Years to Human Years

One cat year does not equal seven human years. Read on for tips on determining your cat’s age and check out a cat years to human years chart.

Catster HQ  |  Mar 6th 2018


A popular misconception is that cats age seven years (in human years) for each calendar year. In fact, feline aging is much more rapid during the first two years of life. A cat reaches the approximate human age of 15 during his first year, then 24 at age 2. Each year thereafter, a cat ages approximately four cat years for every calendar year. Thus, a cat who is 5 in cat years would be approximately 36 in human years.

Note: It should be remembered that a cat who lives outdoors ages far more quickly, perhaps even twice as fast, than an indoor cat. Scroll to the bottom of this article to see a chart for easy comparison.

Indicators of a Cat’s Age

A gray cat yawning and showing his teeth.

A cat’s teeth can indicate a cat’s age. Photography ©Seiichi Tanaka | iStock / Getty Images Plus.

If you’ve taken in a stray or adopted a cat whose age is unknown, there are some ways to determine her age. Here are some things vets check to get a general sense of how old a cat is:

  1. A Cat’s Teeth: Teeth are a great indicator of age. Older cats tend to have more staining than younger cats, assuming the previous owner was negligent in brushing the cat’s teeth. And a kitten’s teeth first come in between two to four weeks; their more permanent set appears at around four months of age. So if you open a cat’s mouth and find permanent, white teeth, the feline is likely to be around a year old. Some yellowing might place the cat between 1 and 2, and tartar build-up on all the teeth indicates that the cat could be between 3 and 5. Missing teeth may mean you have a senior cat on your hands.
  2. A Cat’s Muscle Tone: Younger cats are more likely to have some muscle definition from their higher activity level. Older cats are usually a bit bonier and may have some extra skin hanging or protruding shoulder blades.
  3. A Cat’s Coat: A younger cat usually has a soft, fine coat, whereas an older cat tends to have thicker, coarser fur. A senior cat may display grays or patches of white.
  4. A Cat’s Eyes: Bright, clear eyes without tearing or discharge are common in younger cats. A cat with some cloudiness in their eyes is likely to be 12 years old or so. While inspecting the lens, also examine the iris of the eye. Young cats have smooth irises, while the iris of an old cat can sometimes appear somewhat jagged

A Cat’s Life Span

Felines are generally quite long-lived, though mileage varies depending on owner maintenance and genetic predisposition. In a handful of documented cases, cats have exceeded 30 years in age. Typically, indoor cats may live 12 to 18 years, with many surviving into their 20s. Outdoor cats face greater threat of accident and/or illness, and average roughly 10 years.

Use this cat years chart for a better understanding of cat years to human years: 

Photo: Adegie

Tell us: How old is your cat in human years?

Read more about cat years and a cat’s life on Catster.com: