Cat Age Calculator
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Turn your cat's age in years, months or weeks into human years, with a life-stage label and a 1 to 20 year chart.
Quick answer: a 5-year-old cat is about 33 in human years on Cornell's formula (1 year = 16, 2 years = 21, then 4 per year) and 36 on the common 15 and 24 chart. This cat age calculator takes years, months or weeks, so a 10-month-old kitten and a 15-year-old senior both work.
📐 Formula
Cornell: 16 human years at 1 year, 21 at 2 years, then 21 + 4 × (age − 2). Common chart: 15 at 1 year, 24 at 2 years, then 24 + 4 × (age − 2). Months and weeks are converted to years first (months ÷ 12, weeks ÷ 52.18), and the first two years are filled in a straight line.
How to use the cat age calculator
Enter your cat's age
Type the age and choose Years, Months or Weeks. Decimals such as 2.5 work, and the box accepts up to 30 years.
Pick a conversion method
Cornell counts the first two years as 16 and 21 human years. The common chart uses 15 and 24. After year two, both add 4 human years per year.
Read the human-year result
The calculator shows your cat's age in human years, the other method's figure for comparison, and the age in years and months.
Check the life stage
The AAFP stage appears next to the result: kitten, young adult, mature adult or senior. Use it as a prompt to talk to your vet, not as a diagnosis.
How do you convert cat years to human years?
Treat the first two years as two big steps, then add four human years for each year after that. Cornell University's Feline Health Center puts a 1-year-old cat at about 16 human years and a 2-year-old at 21, then "about four human years" for every cat year after. That is why a cat calculator gives a very different answer from the old seven-to-one rule: a kitten grows up in months, and an adult cat ages slowly.
The page offers two curves because sources disagree on the first two steps. Cornell uses 16 and 21. The chart you see on many vet and pet sites uses 15 and 24. They agree on the pace after year two, so the gap between them stays at 3 human years or fewer at every age. Pick either, and expect the result to be an estimate.
Worked example: a 5-year-old cat in human years
Take a cat that is 5 years old. On Cornell's formula the cat is 21 at its second birthday, then gains 4 for each of the three years after that: 21 + (4 × 3) = 33 human years. On the common chart, 24 + (4 × 3) = 36.
Older cats work the same way. A 10-year-old cat is 53 on Cornell's formula and 56 on the chart. A 12-year-old is 61 or 64, and a 15-year-old is 73 or 76. Cornell's own page gives the same 53, 61 and 73 for those ages.
Cat years to human years chart, 1 to 20 years
Use this chart if you would rather look the answer up than type it in. The stage column follows the age bands of the American Association of Feline Practitioners (AAFP), with the mature band running up to the 10th birthday.
| Cat age | Cornell | Common chart | AAFP life stage |
|---|---|---|---|
| 1 year | 16 | 15 | Young adult |
| 2 years | 21 | 24 | Young adult |
| 3 years | 25 | 28 | Young adult |
| 4 years | 29 | 32 | Young adult |
| 5 years | 33 | 36 | Young adult |
| 6 years | 37 | 40 | Young adult |
| 7 years | 41 | 44 | Mature adult |
| 8 years | 45 | 48 | Mature adult |
| 9 years | 49 | 52 | Mature adult |
| 10 years | 53 | 56 | Senior |
| 11 years | 57 | 60 | Senior |
| 12 years | 61 | 64 | Senior |
| 13 years | 65 | 68 | Senior |
| 14 years | 69 | 72 | Senior |
| 15 years | 73 | 76 | Senior |
| 16 years | 77 | 80 | Senior |
| 17 years | 81 | 84 | Senior |
| 18 years | 85 | 88 | Senior |
| 19 years | 89 | 92 | Senior |
| 20 years | 93 | 96 | Senior |
Cat age in months and weeks
Searches for a cat age calculator in months or weeks make sense, because most kitten questions fall in the first year. Neither Cornell nor the AAFP gives month-level figures, so the calculator spreads the first two years in a straight line. A 6-month-old kitten comes out near 8 human years on Cornell's formula, roughly an elementary-school child.
| Cat age | Cornell | Common chart |
|---|---|---|
| 1 month | 1.3 | 1.3 |
| 2 months | 2.7 | 2.5 |
| 3 months | 4 | 3.8 |
| 4 months | 5.3 | 5 |
| 6 months | 8 | 7.5 |
| 9 months | 12 | 11.3 |
| 12 months | 16 | 15 |
| 18 months | 18.5 | 19.5 |
| 24 months | 21 | 24 |
The straight line is our own simplification. Kittens grow fastest in the first weeks, so treat anything under 12 months as a guide, and ask your vet when feeding, vaccines or neutering depend on the exact stage.
Cat life stages: kitten, young adult, mature adult and senior
The American Animal Hospital Association (AAHA) and the AAFP divide a cat's life into five stages in their 2021 life stage guidelines: kitten (birth up to 1 year), young adult (1 to 6 years), mature adult (7 up to 10 years), senior (10 years and older) and end-of-life, which can happen at any age. The 2021 update cut the earlier six stages down to this simpler set. The guidelines give no human-year equivalents, so the calculator pairs the stage with Cornell's or the common chart's figure.
| AAFP stage | Cat age | Human years, Cornell | Human years, chart |
|---|---|---|---|
| Kitten | Under 1 year | 0 to 16 | 0 to 15 |
| Young adult | 1 to 6 years | 16 to 41 | 15 to 44 |
| Mature adult | 7 to 10 years | 41 to 53 | 44 to 56 |
| Senior | 10 years and older | 53 and up | 56 and up |
How do you find a cat's age from its birthday?
Count the full months since the birthday and enter that number with Months selected. A cat born on March 12 is 19 months old on October 12 of the following year, which comes out at about 19 human years on Cornell's formula. For an exact age in years, months and days from any date, our Age Calculator does the counting, and you can type the result in here.
If you adopted a cat with no known birthday, a vet can estimate its age from its teeth and general condition. Treat that estimate as a range, and enter the middle of it.
Does breed or indoor and outdoor life change a cat's age?
The conversions do not change with breed, and neither does the calculator. Dog calculators adjust for size because small and giant dogs age at different speeds, and our Dog Age Calculator does that. Cats vary far less in size, so one curve is the usual approach. Where a cat lives matters for lifespan and risk, not for the conversion. An indoor cat and an outdoor cat of the same age get the same human-year figure here, though their health checks may differ.
Mistakes to avoid with cat age conversions
- Multiplying by seven. It makes young cats look far younger than they are, and old cats older.
- Treating the life stage as a diagnosis. A cat in the young adult band with a changed appetite still deserves a vet visit.
- Reading the result to the decimal. The curves are rounded published figures, so a 0.3 difference means nothing.
- Switching the method halfway through a comparison. Compare two cats on the same curve.
Signs your cat is entering its senior years
Cornell notes that many cats begin to show age-related physical changes between 7 and 10, and most do by 12. Cornell's list of signs that may suggest a problem includes a loss of appetite and an unkempt coat or skin. None of them is a diagnosis, and a sudden change is a reason for a vet visit at any age.
Food needs shift too. Spayed or neutered adult cats burn fewer calories than intact ones, and an inactive senior needs less again, so recheck the daily amount with our Pet Food Calculator. Own a dog as well? Run its age through the Dog Age Calculator to compare life stages side by side.
Is the cat age calculator different in the UK, Australia and Canada?
No. A cat's age in human years does not depend on the country, so the same conversion applies in the US, UK, Australia and Canada. The AAFP stages are US guidelines, so ask your own vet which age bands and check-up schedule they use.
Frequently asked questions
Give the first year 16 human years, add 5 for the second year, then add 4 for every year after that. A 9-year-old cat works out as 21 + (4 × 7) = 49 on Cornell's curve. For a kitten, choose Months or Weeks in the age box.
No, and the flat rule fails at both ends. It makes a 1-year-old cat 7 where Cornell says about 16, and a 15-year-old cat 105 where Cornell says 73.
About 81 on Cornell's formula and 84 on the common chart. A cat at that age is well into the senior stage, so ask your vet which check-ups suit it.
No. The label marks an age band, not a diagnosis, and plenty of cats stay lively past 10. Ask your vet how often to schedule check-ups as your cat moves from the mature band into the senior one.
Pick Weeks for a kitten under 3 months. A 10-week-old kitten comes out at about 3 human years on Cornell's formula, and a 4-month-old at about 5.
Enter a Maine Coon's age exactly as you would any other cat's. A 4-year-old Maine Coon and a 4-year-old domestic shorthair both come out at 29 on Cornell's formula and 32 on the common chart. If you wonder whether your cat's size changes what to expect as it ages, ask your vet.
Only through health, not the number. A 5-year-old indoor cat and a 5-year-old outdoor cat both read 33 on Cornell's formula and 36 on the common chart. Mention outdoor access, or a strictly indoor routine, when you book a check-up, because your vet can shape vaccines and screening around how your cat lives.
Think of the result as accurate to within a few years. The two curves differ by up to 3 human years, and neither was built from your cat's own health. Your vet's exam says more about your cat's condition than any conversion.
Sources and methodology
The human-year curves come from Cornell University's Feline Health Center (1 year = 16, 2 years = 21, then about 4 per year) and from the widely published 15 and 24 chart, which we could not trace to a single primary source. The life stages come from the 2021 AAHA/AAFP Feline Life Stage Guidelines as summarized by the AAFP. Month and week values are our own straight-line estimates.