Dog age calculator
A dog's age in human years, using the research formula rather than multiplying by seven.
How it works
Converts a dog’s age to the human equivalent using the epigenetic formula from a 2020 study, with size-band adjustment.
The multiply-by-seven rule is wrong, and not slightly. It has no research behind it — the usual explanation is that it began as a marketing device to encourage annual vet visits. It fails worst at both ends: a one-year-old dog is not equivalent to a seven-year-old child but to roughly a thirty-year-old adult, because dogs reach sexual maturity in their first year. And at the far end it overstates, which is why the linear rule produces implausible numbers for old dogs.
The formula here comes from work comparing DNA methylation — chemical marks on DNA that accumulate predictably with age — in Labrador retrievers and humans. It gives human age ≈ 16 × ln(dog age) + 31, a logarithmic curve: fast early, slowing sharply afterwards.
Size matters and the formula does not capture it. Large breeds age faster and die younger, which is unusual — across species, larger animals normally live longer. A Great Dane is elderly at seven while a chihuahua of the same age is middle-aged, so the tool adjusts for size band and says that it is doing so.
This tool runs entirely in your browser. Nothing you enter is sent to a server, logged or stored, and the page keeps working with the network disconnected.
Common questions
- Is one dog year really seven human years?
- No. The rule has no research basis and is thought to have started as a way to encourage annual vet visits. A one-year-old dog is developmentally closer to a thirty-year-old human than a seven-year-old child.
- How is dog age actually calculated?
- The 2020 epigenetic study gives human age ≈ 16 × ln(dog age) + 31, based on DNA methylation patterns. It is logarithmic — rapid early ageing that slows considerably.
- Why do big dogs age faster?
- It is genuinely unusual and not fully explained. Across species larger animals typically live longer; within dogs the opposite holds, so a large breed is elderly at an age when a small one is middle-aged.
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Sources
- Quantitative Translation of Dog-to-Human Aging by Conserved Rate of DNA Methylation — Wang et al., Cell Systems 11(2), 2020