Is a pet’s age really ×7?

No, that’s a myth. Ageing is non-linear: the first year ≈ 15 human years, the second adds ~9 (~24 total), then ~4–5 per year. The calculator uses this curve with a dog-size adjustment.

Why does a dog need a size?

Large and giant breeds age faster and live shorter than small ones. After two years the calculator adds ~4 human years per year for small dogs, ~5 medium, ~6 large and ~7 giant.

Does size matter for cats?

Barely. A cat’s lifespan depends little on size, so a single curve is used: 1 year ≈ 15, 2 years ≈ 24, then +4 per year.

When is a pet considered senior?

Cats and small dogs from about 11 years, large dogs earlier — from 8, giant breeds from 6–7. At that age it’s worth running blood tests once or twice a year.

Is this an exact age?

It’s a reasoned estimate based on veterinary guidelines, not an exact biological age. A vet determines real health by examination and tests.

Cat and dog age in human years

Choose the species, age and (for a dog) breed size — the calculator converts your pet’s age into human years using a science-based non-linear curve and shows the life stage. The “multiply by 7” rule is outdated: the first year counts as about 15 human years, and large dogs age faster than small ones.

Convert your pet’s age to human years

Choose the species and enter the age — the result appears instantly.

Pet life stages

What each stage means — a guide for care and prevention (AAHA/AAFP). In dogs the “senior” stage arrives earlier for larger breeds.

Stage	What it means
Baby	Puppy/kitten: growth, vaccination, socialisation
Young	Active, forming habits
Adult	Prime years, routine check-ups
Senior	Prevention: blood tests once or twice a year
Geriatric	Close monitoring of health and diet

Why “×7” is a myth

The popular “one pet year equals seven human years” rule is wrong: ageing is non-linear. The first year of a cat’s or dog’s life is about 15 human years (the pet becomes a teenager), the second adds about 9 more (~24 by age two), and after that each year is slower — roughly 4–5 human years.

So a 6-month-old kitten is closer to a 10-year-old child than to the “three and a half years” the ×7 formula gives. This calculator uses that curve rather than the outdated multiplier.

Dog size affects ageing

In dogs, lifespan and ageing speed depend heavily on breed size: small dogs live longer and age more slowly, large and giant breeds faster. So after the two-year mark the calculator adds a different number of “human” years: about 4 per year for small dogs and about 7 for giant ones. In cats size barely matters — one curve fits all.

There is also an epigenetic formula (Wang et al., 2019): human age ≈ 16 × ln(dog age) + 31. It describes adult dogs well but doesn’t work for puppies and ignores size, so we use the age-plus-size model from veterinary associations.

Why the “human” age matters

Translating into human years helps you understand your pet’s life stage and adjust care in time: in older animals vets check the kidneys, liver, joints and teeth more often. For large dogs the “senior” stage starts as early as 6–8 years, for cats and small dogs closer to 11. It’s a guide, not a diagnosis: a vet assesses real condition by examination and tests.

Frequently asked questions

No, that’s a myth. Ageing is non-linear: the first year ≈ 15 human years, the second adds ~9 (~24 total), then ~4–5 per year. The calculator uses this curve with a dog-size adjustment.
Large and giant breeds age faster and live shorter than small ones. After two years the calculator adds ~4 human years per year for small dogs, ~5 medium, ~6 large and ~7 giant.
Barely. A cat’s lifespan depends little on size, so a single curve is used: 1 year ≈ 15, 2 years ≈ 24, then +4 per year.
Cats and small dogs from about 11 years, large dogs earlier — from 8, giant breeds from 6–7. At that age it’s worth running blood tests once or twice a year.
It’s a reasoned estimate based on veterinary guidelines, not an exact biological age. A vet determines real health by examination and tests.

Check your pet’s health from its tests

Upload your cat’s or dog’s tests — AI reads the values for the species and points out what to watch.

Decode my pet’s test

This calculator is for reference and information only and gives an estimate based on veterinary guidelines. A vet determines your pet’s real health by examination and tests.