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 the equivalent 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 (This makes the fact that Candy Cat from Peppa Pig is 4 years old seem very strange) and a 6-year-old cat is 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:

Cat Age Calculator

Estimate your cats age in human years.


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In human years your cat is:
- years old.

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 Equivalent Age
1 month1 year
2 months2.5 years
3 months4 years
4 months5 years
5 months6 years
6 months7.5 years
7 months9 years
8 months10 years
9 months11 years
10 months12.5 years
11 months14 years
1 year15 years
1 year, 1 month15 years, 9 months
1 year, 2 months16 years, 6 months
1 year, 3 months17 years, 3 months
1 year, 4 months18 years
1 year, 5 months18 years, 9 months
1 year, 6 months19 year, 6 months
1 year, 7 months20 years, 3 months
1 year, 8 months21 years
1 year, 9 months21 years, 9 months
1 year, 10 months22 years, 6 months
1 year, 11 months23 years, 3 months
2 years24 years
3 years28 years
4 years32 years
5 years36 years
6 years40 years
7 years44 years
8 years48 years
9 years52 years
10 years56 years
11 years60 years
12 years64 years
13 years68 years
14 years72 years
15 years76 years
16 years80 years
17 years84 years
18 years88 years
19 years92 years
20 years96 years
21 years100 years
22 years104 years
23 years108 years
24 years112 years
25 years116 years
26 years120 years
27 years124 years
28 years128 years
29 years132 years
30 years136 years
31 years140 years
32 years144 years
33 years148 years
34 years152 years
35 years156 years
36 years160 years
37 years164 years
38 years*168 years

*the oldest cat who ever lived.

In the first month of your cat’s 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.