🐈 Cat Age Calculator

Convert your cat's age to human years using a commonly cited veterinary age chart — the first year counts for about 15 human years, the second for 9 more, then roughly 4 years per year after that.

The three-stage chart behind the number

Cats do not age on a single multiplier. The calculator uses the piecewise chart vets usually quote: fifteen human years for the first year, nine more for the second, then four a year from there on.

age ≤ 1 yr : human = 15 × age
age ≤ 2 yr : human = 15 + 9 × (age - 1)
age > 2 yr : human = 24 + 4 × (age - 2)

A five-year-old cat is 24 + 4 × 3 = 36 human years. The step at two is why a kitten's birthday moves the figure so much more than a middle-aged cat's: the first two years cover growth, sexual maturity and full skeletal size, and nothing later is packed that densely.

Reading the scale

Cat ageHuman equivalent
6 months7.5
1 year15
2 years24
10 years56
15 years76
20 years96

Enter years, using decimals for kittens - 0.5 for six months, 0.75 for nine. The input accepts 0.1 to 25.

This is a convention for translating age, not a health measure. Breed, body condition, dental disease, and whether a cat lives indoors all move real ageing, and none of them is in the arithmetic. Vets commonly move cats to twice-yearly check-ups around ten; a change in appetite, weight, thirst or litter box habits is a call to your vet whatever the chart says.

Frequently asked questions

How old is a 5 year old cat in human years?

36. The first two years are worth 24 between them, then each further year adds four, so five years is 24 plus three lots of four.

At what age is a cat considered senior?

Around ten to eleven, which this chart puts at 56 to 60 human years. Cats reaching fifteen are in the 76-year band, and plenty live past twenty.

Do indoor and outdoor cats age differently?

The chart makes no distinction - it converts age alone. Life expectancy does differ, largely through traffic, fights and infectious disease rather than a different rate of ageing.