Cat Age Calculator
Find out how old your cat is in human years using the veterinary-approved formula, adjusted for indoor vs outdoor lifestyle.
How Cat Years Work
Cats age differently than dogs or humans. The first year of a cat's life is equivalent to about 15 human years — they go from helpless kitten to a fully mature adolescent. The second year adds roughly 9 more human years, making a 2-year-old cat about 24 in human terms. After that, each additional cat year equals approximately 4 human years.
The Veterinary Formula
This calculator uses the formula endorsed by the American Association of Feline Practitioners (AAFP) and the American Animal Hospital Association (AAHA):
- First year: 15 human years
- Second year: +9 human years (total: 24)
- Each year after: +4 human years
Indoor vs Outdoor Lifespan
Indoor cats typically live 12–18 years, with many reaching their early 20s. Outdoor cats face significantly more risks — cars, predators, diseases, fights with other animals — and their average lifespan is only 5–8 years. Indoor/outdoor cats fall somewhere in between at 8–15 years.
This dramatic difference is why most veterinarians recommend keeping cats indoors or providing a secure outdoor enclosure (catio). An indoor cat at age 15 is a healthy senior, while an outdoor cat at 15 would be exceptionally lucky.
Cat Life Stages
The AAFP defines six life stages for cats: Kitten (0–6 months), Junior (7 months–2 years), Prime (3–6 years), Mature (7–10 years), Senior (11–14 years), and Super Senior (15+ years). Each stage has specific health considerations, from kitten vaccinations to senior bloodwork panels.
Caring for Senior Cats
Cats over 10 years old should see a vet every 6 months instead of annually. Watch for changes in appetite, water intake, litter box habits, and mobility. Early detection of kidney disease, hyperthyroidism, and diabetes can add years to your cat's life.