How to use the cat age calculator
Type your cat's age in years and months, or switch to Date of birth and pick the day your cat was born. For a kitten you can type the whole age in months, such as 0 years and 9 months. The big number is your cat's age in human years. Below it you see the life stage from the 2021 veterinary guidelines, International Cat Care's own stage name, and the age in months. Copy result gives you the lot as text.
How old is my cat in human years?
International Cat Care, the cat welfare charity, puts it simply:
"every year thereafter is equivalent to 4 human years."International Cat Care, How to tell your cat's age in human years
That comes after the first two years, which it counts as 24 human years together. So for a cat aged 2 or more:
Human years = 24 + 4 × (cat's age − 2)
A 9-year-old cat is 24 + 4 × 7 = 52. A 15-year-old cat is 24 + 4 × 13 = 76. The AVMA's own chart gives the same figures for cats aged 1 to 16.
The first two years go much faster, so for kittens the calculator uses the chart's month rows. Between two rows it reads along a straight line: 9 months lies between 7 months (12) and 12 months (15), which gives about 13. The chart ends at 25 years (116); past that the calculator keeps adding 4 a year and says so.
Cat age chart: cat years to human years
International Cat Care's chart, with its own life stage names:
| Cat's age | Human years | Stage (ICC) |
|---|---|---|
| 0 to 1 month | 0 to 1 | Kitten |
| 2 months | 2 | Kitten |
| 3 months | 4 | Kitten |
| 4 months | 6 | Kitten |
| 5 months | 8 | Kitten |
| 6 months | 10 | Kitten |
| 7 months | 12 | Junior |
| 12 months | 15 | Junior |
| 18 months | 21 | Junior |
| 2 years | 24 | Junior |
| 3 years | 28 | Adult |
| 4 years | 32 | Adult |
| 5 years | 36 | Adult |
| 6 years | 40 | Adult |
| 7 years | 44 | Mature |
| 8 years | 48 | Mature |
| 9 years | 52 | Mature |
| 10 years | 56 | Mature |
| 11 years | 60 | Senior |
| 12 years | 64 | Senior |
| 13 years | 68 | Senior |
| 14 years | 72 | Senior |
| 15 years | 76 | Super Senior |
| 16 years | 80 | Super Senior |
| 17 years | 84 | Super Senior |
| 18 years | 88 | Super Senior |
| 19 years | 92 | Super Senior |
| 20 years | 96 | Super Senior |
| 21 years | 100 | Super Senior |
| 22 years | 104 | Super Senior |
| 23 years | 108 | Super Senior |
| 24 years | 112 | Super Senior |
| 25 years | 116 | Super Senior |
Kitten age and cat age in months
Kittens grow up fast. On the chart a 3-month-old kitten is like a 4-year-old child, a 6-month-old like a 10-year-old, and a 1-year-old cat like a 15-year-old teenager. By 2 years a cat is 24 in human years. To find a kitten's age, enter the months: 0 years and 5 months gives 8 human years. If you know the date of birth, use that instead, and the calculator also shows the age in weeks for kittens under 4 months.
Cat life stages
The 2021 AAHA/AAFP Feline Life Stage Guidelines, written by a task force of experts in feline medicine, set four age-based stages and a fifth that is not tied to age:
| Life stage | Age |
|---|---|
| Kitten | birth up to 1 year |
| Young adult | 1 year through 6 years |
| Mature adult | 7 to 10 years |
| Senior | over 10 years |
| End of life | any age |
The guidelines add that age groupings are "arbitrary demarcations along a spectrum and not absolutes." A cat of exactly 10 sits on the line: the guidelines say mature adult runs from 7 to 10 and senior is over 10 (their press release says 10 and older), so the calculator shows mature adult on the 10th birthday and senior from the next day. End of life depends on health, so the calculator never shows it.
International Cat Care uses six names instead: Kitten (to 6 months), Junior (7 months to 2 years), Adult (3 to 6), Mature (7 to 10), Senior (11 to 14) and Super Senior (15 and over). Both are shown, so you can match what your vet or a cat care leaflet says.
Indoor vs outdoor cats
Neither chart gives a different conversion for indoor and outdoor cats. The 2021 guidelines discuss lifestyle as a health matter instead: an indoor-only life may lower the risk of injury and infection but raise others, such as weight gain and behavior problems, while outdoor access brings risks such as injury, poisoning and parasites. They call the plain indoor or outdoor label "oversimplified". International Cat Care says cats live on average for around 12 to 14 years, and some reach their late teens or early twenties.
In Excel or Google Sheets
With a cat's age in years (2 or more) in A2, =24+4*(A2-2) gives the human years. With the date of birth in B2, =DATEDIF(B2,TODAY(),"y") gives the age in whole years, and =DATEDIF(B2,TODAY(),"m") the age in whole months. For a cat born on February 29, this calculator counts February 28 as the birthday in common years; spreadsheets and some other tools may count March 1 instead.
Questions and answers
How do you calculate cat years in human years?
International Cat Care counts the first two years as 24 human years and each year after that as 4. So a cat's human age is 24 + 4 × (age − 2) from 2 years on. Kittens follow the chart's month rows.
How old is a 10-year-old cat in human years?
56 on International Cat Care's chart: 24 + 4 × 8. Under the 2021 AAHA/AAFP guidelines a 10-year-old cat is at the end of the mature adult stage.
How old is a 6-month-old kitten in human years?
About 10, on International Cat Care's chart. A 3-month-old kitten is about 4 and a 1-year-old cat about 15.
At what age is a cat a senior?
The 2021 AAHA/AAFP guidelines call cats senior when they are over 10 years old. International Cat Care's chart uses Senior for 11 to 14 years and Super Senior from 15.
Is one cat year equal to seven human years?
Not on these charts. A cat reaches about 15 in human years in its first year and 24 by its second, then ages about 4 human years a year.
Do indoor cats age more slowly?
The charts do not treat them differently. The 2021 guidelines say indoor and outdoor lifestyles carry different health risks, so ask your vet what your cat's lifestyle means for its care.
Sources
Checked on 8 October 2026. If a rule has changed, please tell us.
- International Cat Care: How old is your cat? (chart, PDF)
- International Cat Care: How to tell your cat's age in human years
- AAHA/AAFP: 2021 Feline Life Stage Guidelines (PDF)
- AAFP: AAHA and AAFP release updated Feline Life Stage Guidelines (press release, PDF)
- AVMA: Pets age faster than people (cat and dog chart, PDF)
- Microsoft Support: DATEDIF function
- Google Docs Editors Help: DATEDIF