What is my cat’s age in human years?
Enter your cat’s birthday, or its age in years and months. The cat age calculator gives its age in human years and its life stage.
- In human years
- 36
A cat of 5 years is about 36 in human years (Young adult).
- Life stage
- Young adult
- Cat’s age
- 5 years
- Age in months
- 60
Answer for the example date Friday, October 2, 2026. It changes to today's date when the page loads.
In human years: 36. A cat of 5 years is about 36 in human years (Young adult).
How to calculate
Converts a cat’s age, from its birthday or in years and months, to human-equivalent years on the AAHA/AAFP feline age chart, and names its life stage.
Example with the default inputs (What do you know? Birthday, Cat’s birthday October 2, 2021, Age on October 2, 2026) on the example date Friday, October 2, 2026: A cat of 5 years is about 36 in human years (Young adult).
Method: human years on straight lines through (0 months, 0), (3, 4), (6, 10), (12, 15), (18, 21), (24, 24); from 24 months, human years = 24 + 4 × (cat years − 2).
- The chart is the AAHA/AAFP and International Cat Care feline age chart: 3 months = 4, 6 months = 10, 12 months = 15, 18 months = 21, 2 years = 24, then 4 human years for each cat year.
- Between the chart’s points, the human age is read on a straight line, by whole months.
- A birthday counts completed months up to the age-on date; days past the last whole month are not counted.
- Life stages follow the 2021 AAHA/AAFP guidelines by completed years: kitten under 1, young adult 1 to 6, mature adult 7 to 10, senior over 10.
- The chart is an average for all cats; it does not depend on breed or size.
Worked examples
Each example is checked against the calculator on every build.
- What do you know? Age, Years 2, Months 0 gives In human years 24, Life stage Young adult, Age in months 24.Source: AAHA/AAFP and International Cat Care feline age chart, as printed by IAMS (https://www.iams.com/cat/cat-articles/calculating-your-pets-age-cat-years, retrieved 2026-10-01): 2 years = 24 human years; 2021 AAHA/AAFP Feline Life Stage Guidelines (https://catvets.com/resource/aaha-aafp-feline-life-stage-guidelines/): young adult 1 to 6 years
- What do you know? Age, Years 10, Months 0 gives In human years 56, Life stage Mature adult.Source: AAHA/AAFP and International Cat Care feline age chart, as printed by IAMS (https://www.iams.com/cat/cat-articles/calculating-your-pets-age-cat-years): 7 to 10 years = 44 to 56
- What do you know? Age, Years 0, Months 9 gives In human years 12.5, Life stage Kitten.Source: AAHA/AAFP and International Cat Care feline age chart, as printed by IAMS (https://www.iams.com/cat/cat-articles/calculating-your-pets-age-cat-years): 6 months = 10, 12 months = 15
- What do you know? Birthday, Cat’s birthday 2011-03-15, Age on 2026-09-30 gives In human years 78, Life stage Senior, Cat’s age 15 years, 6 months, Age in months 186.Source: AAHA/AAFP and International Cat Care feline age chart, as printed by IAMS (https://www.iams.com/cat/cat-articles/calculating-your-pets-age-cat-years): 15 years = 76
How it works
The calculator works in whole months of the cat’s age.
- With a birthday: the age is the completed whole years and months from the birthday to the age-on date (the age-on date is today unless you change it). Days past the last whole month are not counted. Adding months keeps the day of the month; a day past the end of the target month moves to its last day, so a cat born on January 31 is 1 month old on February 28 (or 29).
- With an age: months = 12 × years + months (0 to 40 years, 0 to 11 months).
The chart
The feline age chart from AAHA, AAFP and International Cat Care gives these points:
| Cat’s age | Human years |
|---|---|
| 0 | 0 |
| 3 months | 4 |
| 6 months | 10 |
| 12 months | 15 |
| 18 months | 21 |
| 2 years | 24 |
| 3 years | 28 |
| 7 years | 44 |
| 10 years | 56 |
| 15 years | 76 |
From 2 years on, each cat year adds 4 human years: human years = 24 + 4 × (cat years − 2) = 24 + (months − 24) ÷ 3. Below 2 years, the human age is read on a straight line between the two chart points on either side, by whole months. For example, 9 months is halfway between 6 months (10) and 12 months (15), so it is 12.5.
Life stage
By completed years, from the 2021 AAHA/AAFP Feline Life Stage Guidelines: under 1 year is a kitten, 1 to 6 years a young adult, 7 to 10 years a mature adult, and over 10 years (11 and older in completed years) a senior.
What the calculator shows
- In human years: rounded half up to one decimal place.
- Life stage, the cat’s age in years and months, and the age in months.
Rules
- A birthday after the age-on date has no answer.
- Ages over 40 years have no answer.
Worked examples by hand
2 years. 24 months is the chart point 24: a young adult.
10 years. 24 + 4 × (10 − 2) = 24 + 32 = 56: a mature adult.
9 months. Between 6 months (10) and 12 months (15): 10 + (15 − 10) × (9 − 6) ÷ (12 − 6) = 10 + 2.5 = 12.5: a kitten.
Born March 15, 2011, on September 30, 2026. 15 years to March 15, 2026, then 6 months to September 15, 2026, and 15 days left over: 15 years 6 months, or 186 months. Human years = 24 + (186 − 24) ÷ 3 = 24 + 54 = 78: a senior.
Other questions people ask
How do I convert cat years to human years?
The first year of a cat’s life equals about 15 human years, the second adds 9 more (24 at age 2), and each year after that adds about 4. A 10-year-old cat is about 24 + 4 × 8 = 56 in human years.
Is one cat year equal to seven human years?
No. Cats grow up fast: a 1-year-old cat is closer to a 15-year-old person. After age 2 the pace slows to about 4 human years per cat year, so the seven-year rule is wrong at both ends.
What are the life stages of a cat?
The 2021 AAHA/AAFP Feline Life Stage Guidelines use kitten (birth up to 1 year), young adult (1 to 6 years), mature adult (7 to 10 years) and senior (over 10 years), plus end of life, which can come at any age.
When is a cat a senior?
After age 10, by the 2021 AAHA/AAFP guidelines. That is about 60 in human years. Vets suggest more frequent check-ups from this age.
How old is a 6-month-old kitten in human years?
About 10. The chart puts 3 months at about 4, 6 months at about 10 and 12 months at about 15 human years.
Does breed change a cat’s age in human years?
The chart does not use breed or size; it is an average for all cats. Unlike dogs, cats vary little in size, so one chart is the usual rule.
What if I do not know my cat’s birthday?
Choose Age and type your best guess in years and months. A vet can estimate a cat’s age from its teeth, eyes and coat.