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A guide based on standard veterinary charts. Individual dogs age differently; breed, weight and health matter more than any formula.
What The Dog Age Calculator Works Out
- Human age equivalent: the first dog year counts as 15 human years and the second as 9, then each further year adds 4 (small), 5 (medium), 6 (large) or 7 (giant) human years. The old "multiply by seven" rule is wrong at both ends: a one-year-old is already a teenager, while a 10-year-old Jack Russell is about 56 and a 10-year-old great dane about 80.
- Life stage: puppy to 1, young adult 1 to 3, adult 3 to 7, senior from 7 (from 5 for giant breeds, which age fastest and live shortest). Diet, exercise and vet care should change with the stage rather than the number.
- Chart table: the same formula for 1 to 14-year-old dogs in all four size classes, so you can see how small dogs mature faster early on but then age more slowly and live longer.
- Extra months (advanced): adds months to the whole years so a dog of 5 years 8 months is aged as 5.67 years rather than 5.
- Human years per dog year (advanced): overrides the size default for the years after age 2. Useful for breeds that sit at the edge of a class, such as a 22kg collie that behaves more like a large dog, or if your vet uses a different chart.
- Epigenetic estimate (advanced): the DNA methylation formula from the 2020 UCSD study: 16 times the natural log of the dog's age, plus 31. It agrees that puppies age astonishingly fast (a 1-year-old scores 31) but flattens later, and was developed mainly on labradors, so treat it as a second opinion.
- Share of typical lifespan (advanced): the dog's age as a percentage of a typical lifespan of 14 years (small), 12.5 (medium), 11 (large) or 9 (giant), or a lifespan you enter for the breed. Ticking neutered adds about a year, in line with UK insurance and veterinary data. Averages only: plenty of dogs live well past them.
- Human age at next birthday (advanced): shows how many human years the next dog year adds, which is the figure that explains why a senior dog can change noticeably within one calendar year.
- Vet check-ups (advanced): suggests annual checks for adults, twice-yearly for seniors and frequent visits for puppies, and works out when the next is due from the months since the last one. UK vets recommend twice-yearly check-ups for large breeds from middle age onwards.
- Milestone table (advanced): the dog age at which this dog reaches each human milestone (21, 30, 40 and so on up to 90) and how far away each is. This is a guide, not veterinary advice.
Source and further reading: PDSA pet health advice.