Dog Age Calculator

What is a Dog Age Calculator?

A Dog Age Calculator converts your dog's age in years into an approximate human age using a modern, size-aware formula. Small, medium and large breeds age at different rates, so the tool lets you pick the right size before estimating.

How is the age estimated?

The common formula counts the first year as about 15 human years, the second year as another 9, and then adds 4 to 5 human years per year depending on size. A 3-year-old medium dog therefore equals ≈15 + 9 + 4 = 28 human years.

Is my data safe?

Yes. The estimate is calculated entirely in your browser; the age and size you enter are never sent or stored. Free, no signup and completely client-side.

Why 'one year equals seven' is wrong

Dogs age fast in their first two years — the first year matches roughly 15 human years, the second about 9 more — then the pace slows. The old rule overstates young dogs and understates seniors, so most modern charts use a two-phase scale.

Size and breed shift the numbers

Large breeds reach adulthood earlier and age sooner; small dogs often live longer. The result is an estimate, not a diagnosis — regular vet checks matter far more than a precise human-age number.