Is one dog year really seven human years?

No. A 2020 study of Labrador DNA found dogs age very quickly at first and then slow down: human age ≈ 16 × ln(dog age) + 31. A 1-year-old dog is roughly 31 in human terms, a 4-year-old about 53 and a 12-year-old about 71.

How old is my cat in human years?

A cat is about 15 at their first birthday and 24 at their second, then ages about four human years for every year after that. A 10-year-old cat is roughly 56 and a 15-year-old roughly 76.

When is a dog a senior?

Vets define senior as the last quarter of a dog's expected lifespan, so it depends on breed and size. UK dogs live 11.23 years on average (VetCompass, 2022), which puts the start of the last quarter at about 8.5; breeds with shorter average lives get there sooner.

When is a cat a senior?

The 2021 AAHA/AAFP feline guidelines class cats as kittens up to 1, young adults from 1 to 6, mature adults from 7 to 10 and seniors over 10. Cats Protection calls cats mature from 7 and senior from 11.

Does breed or size change the dog formula?

The formula was built from Labradors, a medium-to-large breed, so it is a guide rather than an exact figure for every dog. Giant breeds generally age faster and small breeds slower; your vet will factor that in.

Quick answer

A 1-year-old dog is roughly 31 in human years and a 1-year-old cat roughly 15. Dogs then age more slowly (a 10-year-old is about 68); cats add about four human years for every year after their second birthday (a 10-year-old is about 56). Life stage matters more than the number: it decides how often your vet wants to see them.

Dog and cat age calculator

Convert your pet's age into human years using published research rather than the old “times seven” rule — then see which life stage they are in and what vets focus on at that age.

A population average, not a health check. Your vet judges life stage from the whole animal. See our senior pet care guide.

How the calculator works

Dogs use the formula from a 2020 study that compared age-related DNA changes in 104 Labradors with those in people: human age = 16 × the natural log of the dog's age + 31. It lines up with real milestones: an 8-week-old puppy matches a baby of about 9 months, when both are cutting milk teeth. We don't convert puppies younger than 8 weeks.

Cats use the widely used conversion that UK insurers such as Agria publish: 15 at one year, 24 at two, then four human years per cat year.

Life stages follow the American Animal Hospital Association and American Association of Feline Practitioners guidelines, which vets use worldwide. We never estimate how long your pet has left: a breed average isn't a forecast for one animal.

Sources

Frequently Asked Questions

Is one dog year really seven human years?: No. A 2020 study of Labrador DNA found dogs age very quickly at first and then slow down: human age ≈ 16 × ln(dog age) + 31. A 1-year-old dog is roughly 31 in human terms, a 4-year-old about 53 and a 12-year-old about 71.
How old is my cat in human years?: A cat is about 15 at their first birthday and 24 at their second, then ages about four human years for every year after that. A 10-year-old cat is roughly 56 and a 15-year-old roughly 76.
When is a dog a senior?: Vets define senior as the last quarter of a dog's expected lifespan, so it depends on breed and size. UK dogs live 11.23 years on average (VetCompass, 2022), which puts the start of the last quarter at about 8.5; breeds with shorter average lives get there sooner.
When is a cat a senior?: The 2021 AAHA/AAFP feline guidelines class cats as kittens up to 1, young adults from 1 to 6, mature adults from 7 to 10 and seniors over 10. Cats Protection calls cats mature from 7 and senior from 11.
Does breed or size change the dog formula?: The formula was built from Labradors, a medium-to-large breed, so it is a guide rather than an exact figure for every dog. Giant breeds generally age faster and small breeds slower; your vet will factor that in.