Cat Age Calculator
Enter your cat's age in years to get its human age equivalent, using the standard veterinary aging chart. You'll also see its life stage and how many human years it's aging this year.
How to calculate cat age
This is the chart used by most veterinary sources (ASPCA, PetMD, International Cat Care): a cat reaches roughly 15 human years by its first birthday and 24 by its second, then ages at a steady rate of about 4 human years for every year after. Unlike a dog's aging curve, which keeps flattening out, a cat's pace levels off early and stays fairly constant, so the "human years gained this year" figure holds at about 4 for the rest of its life instead of shrinking.
Year 1 = 15 human years, year 2 adds 9 more (24 total), then +4 per year after that
Worked example
A cat is 6 years old.
- Past year 2, so use 24 + 4 × (age - 2)
- 24 + 4 × (6 - 2) = 24 + 16 = 40 human years
- Last year's age was 24 + 4 × (5 - 2) = 36, so this year added 4.0 human years
Result: 40 human years old, in the "adult" life stage, aging 4.0 human years this year
Frequently asked questions
How do I convert cat years to human years?
Use the standard veterinary chart: a 1-year-old cat is about 15 human years, a 2-year-old is about 24, and every year after that adds roughly 4 more human years. So a 10-year-old cat works out to 24 + 4 × 8 = 56 human years.
Why do cats age so much in the first two years?
A cat reaches physical and sexual maturity by around 12 months, similar to a human teenager, and is essentially a young adult by 2 years old. That rapid early development is why the first two "cat years" are worth 15 and then 9 more human years, far more than any later year.
At what age is a cat considered a senior?
This calculator uses 11 years as the senior threshold, matching the widely used International Cat Care life-stage guidelines (kitten, junior, prime, mature, then senior at 11+). Cats often stay active and healthy well into their teens, so "senior" here means an age to start watching more closely, not old age.
Do indoor cats age differently from outdoor cats?
The chart itself doesn't change, but indoor cats typically live longer (often 13 to 17 years versus a shorter average for outdoor cats) because they face fewer accidents, predators, and diseases. A longer lifespan just means more years spent at the flatter, +4-per-year part of the curve.
Is a cat's aging curve different from a dog's?
Yes. Both mature quickly in their first two years, but a dog's aging rate keeps slowing down for life (see the dog age calculator), while a cat's pace levels off early and then stays close to a steady 4 human years per year. That's why this calculator's "years gained this year" figure holds steady for cats but keeps shrinking for dogs.