How To Work Out Cat Age In Human Years

Cats age much faster than humans in their first couple of years.

A one-year-old cat is roughly equivalent to a 16-year-old human. In their second year they mature at a slightly slower rate with a two year old cat being equivalent the of a 24 year old human.

After cats have matured a slower rate of 4 cat years to every human year is a more accurate scale. With a 4 year old cat being the equivalent of a 32 year old human and a 6 year old cat being the equivalent of a 40 year old human.

Indoor cats live to an average of 15 years which is equivalent to a human age of 76.

Cat Age Calculator:

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  45. 168 Years

Cat Age In Human Years Conversion Table

While it is not an exact science the table below shows how cats mature at a much faster rate than humans do:

Cats AgeHuman EquivalentLife Stage
1 month1 yearKitten
2 months3 yearsKitten
3 months5 yearsKitten
4 months7 yearsKitten
5 months9 yearsKitten
6 months11 yearsKitten
12 months16 yearsYoung Adult
18 months20 yearsYoung Adult
2 years24 yearsYoung Adult
3 years28 yearsPhysical Prime
4 years32 yearsPhysical Prime
5 years36 yearsPhysical Prime
6 years40 yearsPhysical Prime
7 years44 yearsMature
8 years48 yearsMature
9 years52 yearsMature
10 years56 yearsOld
11 years60 yearsOld
12 years64 yearsOld
13 years68 yearsOld
14 years72 yearsOld
15 years76 yearsVery old
16 years80 yearsVery old
17 years84 yearsVery old
18 years88 yearsVery old
19 years92 yearsVery old
20 years96 yearsVery old
21 years100 yearsVery old
22 years104 yearsVery old
23 years108 yearsVery old
24 years112 yearsVery old
25 years116 yearsVery old
38 years*168 yearsVery old

*the oldest cat who ever lived.

In the first month of your cats life they mature by the equivalent of one human year.

Over the next few months the rate at which they mature speeds up to two human years for every month of your cat’s life.

By the age of 6 months old they are equivalent to an 11-year-old human.

Once they reach the age of 6 months old the rate of maturing slows down, with cats maturing at a more leisurely rate of 4 human years to every 6 months.

By the time they reach 18 months old they are fully grown and are equivalent to a 20-year-old human.

The 6 months / 4 year rate continues until they are two years old (24 years old in human years).

From here on your cat will age by 4 human years for every one cat year.

A few landmark cat ages and their human equivalent include:

  • 3.5 cat years = 30 human years
  • 6 cat years = 40 human years
  • 8.5 cat years = 50 human years
  • 10 cat years = 56 human years
  • 11 cat years = 60 human years
  • 21 cat years = 100 human years

The average cat will live to the age of 15 years, the equivalent of 76 in human years.

The record for the oldest cat is 38 years, a massive 168 years in human years.

The average outdoor cat will live to 5.5 years, equivalent to a 38 year old human.


Not sure how old your cat is? Read our article on how to tell a cats age.

Adopted an old cat?
Cats over the age of 10 can be very expensive to insure and it can be difficult to get comprehensive cover for them.

Read our guide to cat insurance for older cats to find a good deal.

Average Cat Life Expectancy

Cats life expectancies vary from breed to breed, things such as whether they have been neutered also impact their life expectancy.

indoor cat chilling

As a general rule mixed breed cats are often hardier and have longer than average life spans.

The factor which has the biggest impact on the length of your cats life is whether it is an indoor or an outdoor cat:

  • An indoor cat can expect to live to an average of 15 years.
  • Outdoor cats live an average of 5.5 years.

Read our article on how long do cats live for more information.

The human age equivalent of a 15 year old cat is 76.

How Is Cat Age In Human Years Calculated?

76 is the average lifespan for humans globally (it is closer to 80 in the western world).

Cat ages in human years are calculated based on average lifespans.

For example 76/15 = 5, meaning that one human year equals 5 cat years. With a bit of adjustment to accomodate the faster rates of maturing as kittens we get to the figures above.

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