Short answer: a cat’s first year equals about 15 human years, and the second year adds about 9 more, so a 2-year-old cat is roughly 24. After that, each cat year adds about 4 human years. A 10-year-old cat is around 56 in human terms, and a 15-year-old is around 76. Unlike dogs, cats of different breeds and sizes are usually converted with the same formula.
Below you’ll find a cat-years-to-human-years chart from 3 months to 25 years, how the math works, the life stages veterinarians actually use (kitten, young adult, mature adult and senior), and what each stage means for your cat’s care.
Cat age in human years chart
The figures use the same formula as our Pet Age Pro app, rounded down to whole years. The life stage column follows the 2021 AAHA/AAFP Feline Life Stage Guidelines.
| Cat’s age | Human years | Life stage (AAHA/AAFP) |
|---|---|---|
| 3 months | 3 | Kitten |
| 6 months | 7 | Kitten |
| 9 months | 11 | Kitten |
| 1 year | 15 | Young adult |
| 18 months | 19 | Young adult |
| 2 years | 24 | Young adult |
| 3 years | 28 | Young adult |
| 4 years | 32 | Young adult |
| 5 years | 36 | Young adult |
| 6 years | 40 | Young adult |
| 7 years | 44 | Mature adult |
| 8 years | 48 | Mature adult |
| 9 years | 52 | Mature adult |
| 10 years | 56 | Mature adult / senior |
| 11 years | 60 | Senior |
| 12 years | 64 | Senior |
| 13 years | 68 | Senior |
| 14 years | 72 | Senior |
| 15 years | 76 | Senior |
| 16 years | 80 | Senior |
| 17 years | 84 | Senior |
| 18 years | 88 | Senior |
| 19 years | 92 | Senior |
| 20 years | 96 | Senior |
| 21 years | 100 | Senior |
| 22 years | 104 | Senior |
| 25 years | 116 | Senior |
The guidelines place 10-year-olds at the boundary: mature adult runs from 7 to 10, and senior starts at 10. Ages over 100 simply mean the cat has lived well beyond a typical lifespan.
How to calculate your cat’s age in human years
The calculation has three steps:
- Year one counts as 15 human years. A kitten goes from newborn to nearly adult size in that time, a bit like a child growing into a teenager.
- Year two adds 9 more, for a total of 24. By then most cats are fully mature.
- Every year after that adds 4.
For a quick estimate of an adult cat: take the cat’s age, subtract 2, multiply by 4, and add 24.
Example: a cat who is 8½ years old. Year one gives 15, year two adds 9 (total 24), and the remaining 6½ years add 6.5 × 4 = 26. That makes 50 in human terms.
This 15 / 9 / 4 pattern is the conversion veterinary sources commonly cite. PetMD, for example, credits it to the American Veterinary Medical Association.
Does breed or size change the numbers?
For dogs, size makes a big difference, which is why our dog age in human years chart has separate columns for small, large and giant breeds. Cats vary much less in size, so the same conversion is used for all of them, and Pet Age Pro applies one formula to every cat breed.
Breed can still affect how long a cat is likely to live. A 2024 study of 7,936 cats in the UK (published in the Journal of Feline Medicine and Surgery) found an average life expectancy of 11.74 years. Burmese cats had the longest life expectancy of the breeds studied, at 14.42 years, and Sphynx cats the shortest, at 6.68 years. Male cats lived about 16 months less than females on average. These are averages for one country’s vet-clinic population, and plenty of cats live well into their late teens or beyond.
Why “one cat year equals seven human years” is wrong
The seven-year rule would make a 1-year-old cat the equivalent of a 7-year-old child. In reality, most cats are nearly full-grown and can reproduce before their first birthday, which is much closer to a human teenager. Later in life the rule overshoots: it turns a 12-year-old cat into an 84-year-old, while the 15 / 9 / 4 conversion puts that cat at about 64.
The real pattern is fast ageing early on, then a slower, steady pace. That’s why a single multiplier doesn’t work.
Cat life stages: what vets use
Human-year equivalents are a helpful picture, but veterinarians plan care around life stages. The 2021 AAHA/AAFP Feline Life Stage Guidelines, written by the American Animal Hospital Association and the American Association of Feline Practitioners, describe four age-based stages, plus an end-of-life stage that can happen at any age:
- Kitten (birth to 1 year): rapid growth, socialization, the kitten vaccine series, parasite control and decisions about spaying or neutering.
- Young adult (1 to 6 years): the cat reaches full size and maturity. This is the stage to set good habits: a healthy weight, dental care and a routine of yearly check-ups.
- Mature adult (7 to 10 years): often still active and healthy on the outside, but this is when weight gain, dental disease and early signs of age-related illness tend to show up.
- Senior (over 10 years): age-related conditions become more common, and cats need closer monitoring.
Earlier guidance split these into more stages (for example “prime,” “mature” and “geriatric”), and you’ll still see those names in older charts. The current guidelines simplified them to the four above.
How Pet Age Pro labels life stages: the app shows “kitten” under 1, “adult” from 1 to 7, and “senior” from 7 onward. That earlier senior label lines up with the start of the guidelines’ mature adult stage, which is when many cats begin to benefit from closer attention to weight, teeth and routine blood work. If your vet uses the four-stage system, a 7- to 10-year-old cat is a “mature adult” rather than a senior.
Know your cat’s age in human years at a glance
Pet Age Pro works out your cat’s human-age equivalent and life stage from their birthday, keeps dogs and cats in one place, and can remind you about birthdays and vet check-ups.
Learn more about Pet Age Pro · Free on Android. iPhone version coming soon.
Using your cat’s age to plan care
- Check-up frequency. Healthy young and mature adult cats generally need a wellness exam at least once a year. For seniors, the AAHA/AAFP guidelines recommend an exam at least every six months for cats aged 10 to 15, and every four months for cats over 15, more often if the cat has a chronic condition.
- Weight. Gradual weight gain is common in young and mature adults, and unexplained weight loss is a common early sign of illness in older cats. Weighing your cat regularly makes both easier to spot.
- Teeth. Dental disease becomes more common with age and is easy to miss, because cats often keep eating despite mouth pain. Ask your vet to check your cat’s teeth at every visit.
- Home comforts for older cats. Cornell’s Feline Health Center notes that older cats tend to be less active, sleep more and may have trouble reaching favorite spots. Low-sided litter boxes, steps or ramps up to a favorite window, and food and water on the same floor where your cat spends the most time can all help.
Cats are also living longer than they used to. Cornell points out that cats were once considered seniors at eight, while today they are generally considered older at 12 to 14.
How vets estimate an adopted cat’s age
If you adopted a cat with an unknown birthday, your veterinarian can give you a rough estimate from physical signs such as the teeth (which are most reliable in kittens and young cats), the coat, muscle condition and the eyes. In adult cats the estimate becomes a range rather than an exact number. Once you have a best guess, you can use it as your cat’s birthday for the chart above and for planning check-ups.
When to call your vet
Growing older isn’t a disease, and Cornell stresses that changes in an older cat shouldn’t be written off as “just age,” because many have treatable causes. Contact your veterinarian if you notice:
- Drinking or urinating more than usual, or changes in litter box habits
- Weight loss or gain, or a change in appetite
- Vomiting, diarrhea or constipation that keeps coming back
- Bad breath, drooling or dropping food
- Stiffness, reluctance to jump, or no longer using high places
- Hiding, confusion, loud crying at night or other changes in behavior or sleep
This guide is general information and isn’t a substitute for advice from a veterinarian who knows your cat.
FAQ
How old is a 1-year-old cat in human years?
About 15. Most cats are close to full size by their first birthday, which is similar to a human in their mid-teens.
How old is a 10-year-old cat in human years?
About 56. The first two years count as 24 human years, and each of the next eight years adds 4.
At what age is a cat considered a senior?
The 2021 AAHA/AAFP Feline Life Stage Guidelines consider cats senior from about 10 years. Cats aged 7 to 10 are classed as mature adults.
Is one cat year equal to seven human years?
No. Cats age much faster than that in their first two years, reaching roughly 24 human years by age 2, and then add about 4 human years per year.
Do indoor cats age more slowly?
No. The conversion is the same for every cat. Lifestyle affects risks such as injury and infectious disease, and so can affect how long a cat lives, but it doesn’t change the human-age equivalent of a given age.
Sources
- American Veterinary Medical Association, JAVMA News. AAHA, AAFP update feline life stage guidelines (2021).
- American Association of Feline Practitioners. Updated senior care guidelines (visit frequency for senior cats).
- Cornell University College of Veterinary Medicine, Cornell Feline Health Center. Loving care for older cats.
- Teng KT, et al. Life tables of annual life expectancy and risk factors for mortality in cats in the UK. Journal of Feline Medicine and Surgery, 2024. Royal Veterinary College repository.
- PetMD (veterinarian-reviewed). How old is my cat in human years?
Written by Jordan Ellis for AppSphere Solutions. Researched against the veterinary and scientific sources listed above. See how we research our guides, or browse more pet care guides.