Convert a dog's age to human-equivalent years with the vets' size-curve model, not the old multiply-by-7 rule, plus a reverse mode and an aging chart.
The conversion happens locally in your browser. Nothing ever leaves your device.
Pick the breed's expected adult weight class — it sets the aging slope after year two.
Fun fact that humbles every chart: two dogs of the same litter can age differently. Brachycephalic (flat-faced) breeds and some purebreds skew the averages — this is a class curve, not a breed oracle.
These are estimates from a population-level curve, not veterinary advice. For health questions, ask your vet.
This calculator uses the size-curve model most veterinary sources describe, not the old ×7 rule. A dog's first two years are compressed on the human timeline: year one lands at about 15 human-equivalent years and year two adds roughly 9 more (about 24). After that the clock slows to a per-year slope that depends on adult size class: Toy +4, Small +4, Medium +5, Large +6, Giant +7. Below age two the curve is interpolated linearly within each of those first two segments. Fractional ages use the same segments, so a 3.5-year-old medium dog is 24 + 1.5 × 5 = 31.5 human-equivalent years.
Because dogs do not age at a constant 7:1 ratio. A dog matures extremely fast in its first two years — roughly equivalent to a 15-year-old human after year one and a 24-year-old after year two — and only then settles into a slower, size-dependent pace of about 4 to 7 human years per dog year. A linear ×7 would call a one-year-old dog a 7-year-old child, which no veterinarian would accept.
Most veterinary sources publish size-based curves like the one used here: the first two years follow a shared fast-maturation path (about 15, then 24 human-equivalent years), after which small breeds add roughly 4 human years per dog year, medium 5, large 6 and giant breeds about 7. It is a consensus approximation, not a laboratory measurement, so treat results as ballparks.
This page only covers dogs. Cat aging follows a different curve (a common rule of thumb puts a one-year-old cat near a 15-year-old human, but the later years differ), so do not reuse the numbers here for a cat — and we do not yet have a separate cat tool to point you at.
Nothing alarmed: the stage badge is a communication aid, not a medical verdict. Senior-equivalent age is a good moment to talk to your veterinarian about check-up frequency, dental care, joint support and diet. Only your vet, examining your actual dog, can tell you what its body is doing.
No. The conversion and the chart are computed locally in your browser with plain JavaScript. Your dog’s age, breed class and results never leave your device, and there is no account and no network request attached to a calculation.
If you just finished with Dog Age Calculator, the natural next steps are Chinese Zodiac Calculator, Age Calculator, BMI Calculator, or browse every tool in Health Tools.