Guide · Updated November 2026 · How we check our numbers

Dog Years to Human Years: Why "Times 7" Is Wrong

The old rule that one dog year equals seven human years is easy to remember — and wrong. Dogs age very quickly at first and more slowly later.

The newer formula

A 2020 study from UC San Diego compared DNA changes in dogs and people and suggested: human age = 16 × ln(dog age) + 31. A 4-year-old dog works out to about 53 human years, and a 1-year-old to about 31.

Size matters

Large and giant breeds generally have shorter lives than small breeds, so they reach "senior" status earlier. Any formula is only a guide.

Cat years

A common rule counts a cat's first year as about 15 human years, the second as about 9 more, and each later year as about 4. A 6-year-old cat is about 40 in human years.

Why it matters

Knowing your pet's life stage helps you plan care: more frequent vet visits for seniors, adjusted calories as activity drops, and watching for joint and dental problems.

Try the calculators

This guide is general information, not professional advice.