How cat years convert to human years
The old "multiply by seven" rule doesn't fit cats at all. Cats grow up fast: by their first birthday they're roughly as developed as a 15-year-old person, and by two they're comparable to a 24-year-old adult. After that, aging slows to a steady pace of about 4 human years for every cat year.
This calculator uses the age-equivalence chart published with the 2021 AAHA/AAFP Feline Life Stage Guidelines, the reference most vets use. For kittens under two, it interpolates between the chart's points (about 1 human year at 1 month, 4 at 3 months, 10 at 6 months, 15 at 12 months and 21 at 18 months).
The formula
age 2 years = 24 human years
over 2: human age = 24 + 4 × (cat age in years − 2)
Example: a 4-year-old cat
| Step | Result |
|---|---|
| First two years | 24 |
| Two more years × 4 | +8 |
| Human-equivalent age | 32 years |
| Life stage | Young adult (mature adult in 3 years) |
Cat age chart, 1 to 20 years
| Cat age | Human age | Life stage |
|---|---|---|
| 1 | 15 | Young adult |
| 2 | 24 | Young adult |
| 3 | 28 | Young adult |
| 4 | 32 | Young adult |
| 5 | 36 | Young adult |
| 6 | 40 | Young adult |
| 7 | 44 | Mature adult |
| 8 | 48 | Mature adult |
| 9 | 52 | Mature adult |
| 10 | 56 | Mature adult |
| 11 | 60 | Senior |
| 12 | 64 | Senior |
| 13 | 68 | Senior |
| 14 | 72 | Senior |
| 15 | 76 | Senior |
| 16 | 80 | Senior |
| 17 | 84 | Senior |
| 18 | 88 | Senior |
| 19 | 92 | Senior |
| 20 | 96 | Senior |
The four feline life stages
- Kitten (birth to 1 year): rapid growth, vaccinations, spay or neuter, and learning to accept handling and carriers.
- Young adult (1 through 6 years): the time to set healthy habits: a lean body weight, dental care and yearly exams.
- Mature adult (7 through 10 years): weight gain and dental disease become more common; some vets start routine bloodwork.
- Senior (over 10 years): watch for kidney disease, hyperthyroidism, arthritis and weight loss. Twice-yearly checkups are recommended.
The guidelines also describe an end-of-life stage, which can happen at any age and focuses on comfort and quality of life. Where exactly a cat turns "senior" is a guideline, not a switch: the source says "over 10 years," so this calculator starts the senior stage just after the 10th birthday, and your vet may treat a fit 11-year-old like a mature adult.
Keep in mind
Human-year equivalents are a comparison tool, not a biological measurement. Genetics, diet, weight and indoor versus outdoor life all change how a particular cat ages. Changes in appetite, thirst, litter box habits or weight are worth a vet visit at any age.
This calculator is for general information and is not veterinary advice.
Frequently asked questions
How old is my cat in human years?
Using the chart from the AAHA/AAFP feline life stage guidelines, a 1-year-old cat is about 15 in human years, a 2-year-old is about 24, and each year after that adds roughly 4 human years. So a 5-year-old cat is about 36 and a 10-year-old is about 56.
Is one cat year equal to seven human years?
No. The seven-to-one rule is a myth. Cats mature very quickly in their first two years, reaching adulthood by about age 2, then age at a slower, steadier pace of about 4 human years per cat year.
At what age is a cat considered a senior?
The 2021 AAHA/AAFP Feline Life Stage Guidelines define senior cats as those over 10 years old. Mature adults are 7 to 10 years, young adults 1 to 6 years, and kittens are under 1 year. Individual cats vary, and a healthy 11-year-old may be treated like a mature adult by your vet.
How long do indoor cats live?
Many indoor cats live into their mid-teens, and it is common for well-cared-for cats to reach 18 to 20 years. Outdoor cats face more risks from traffic, predators and disease and tend to have shorter lives on average.
How can I tell how old a cat is if I don't know its birthday?
A vet can estimate age from teeth, eyes, coat and muscle tone. Kittens can be aged fairly precisely by tooth eruption, while adult age estimates are rougher, often a range of several years.
Rates and figures last checked September 2026.
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