Pet Age Calculator

1. 1Choose Dog or Cat.
2. 2Enter your pet's age in years and months.
3. 3For a dog, choose the breed — or choose by weight for a mixed breed.
4. 4Read the human-equivalent age, life stage and the full chart for that size.

The old rule that one dog year equals seven human years is wrong in both directions. Dogs mature very quickly — a one-year-old dog is roughly as developed as a teenager — and then age more slowly, at a pace that depends on size.

For dogs the calculator uses the size-based chart widely used by veterinary practices: the first year counts as about 15 human years (12 for giant breeds), the second adds about 9, and each year after that adds from 4 years for small dogs to 7 for giant ones. Breeds are grouped by typical adult weight — small up to 9 kg (20 lb), medium to 23 kg (50 lb), large to 45 kg (100 lb) and giant above that — and ages between whole years are interpolated.

It also shows a newer estimate from a 2020 study by researchers at the University of California, San Diego, who compared age-related chemical marks on DNA in Labrador retrievers and people: human age ≈ 16 × ln(dog age) + 31. It was measured in one breed, so treat it as an interesting comparison rather than the answer.

For cats the calculator follows International Cat Care's chart: a cat is about 15 in human terms at one year and 24 at two, and each year after that adds about four human years.

A 6-year-old Labrador Retriever

1. Labradors are large dogs.
2. The large-dog chart gives 45 human years at age 6.
3. The DNA formula gives 16 × ln 6 + 31 = 59.7.

Result: About 45 in human years by the size chart, or about 60 by the DNA-based formula.