--- title: "Dog Age Calculator: Dog Years to Human Years | Good Pet Day" description: "How old is your dog in human years? Compare the vets' size chart with the 2020 DNA formula, see your dog's life stage, and learn why the two disagree." url: https://goodpetday.me/ --- # How old is my dog in human years? Two answers from two kinds of science: the size chart vets have used for years, and a 2020 formula based on changes in DNA. Enter your dog's age and adult size. ## Two numbers, and why they disagree The **size chart** is the one the American Veterinary Medical Association (AVMA) publishes for pet owners. It counts a dog's first year as about 15 human years and the second as about 9 more. After that it adds 4 human years for each birthday in small dogs and up to 7 or 8 in giant breeds, because bigger dogs age faster and usually live shorter lives. The **DNA formula** comes from a 2020 study by Tina Wang and colleagues at the University of California San Diego. They compared chemical marks on DNA that build up with age (methylation) in people and in dogs, and matched them: human age ≈ 16 × ln(dog age) + 31. By this measure dogs race through their early years, so a 1-year-old is like a 31-year-old, then slow down. It was built from Labrador retrievers only, so it does not adjust for size. Neither is exact. The chart is handy for everyday comparisons; the formula is a reminder of how quickly young dogs grow up. For care, the life stage matters most. The American Animal Hospital Association (AAHA) counts a dog as a puppy until rapid growth ends at about 6–9 months, a young adult until about 3–4 years, then a mature adult until the last quarter of the expected lifespan, when the senior years begin. The AVMA puts that at about 8–11 years for small dogs, 8–10 for medium, 8–9 for large and 6–7 for giant breeds. ## Sources - AVMA, [Caring for senior cats and dogs](https://www.avma.org/resources-tools/pet-owners/petcare/senior-pets) and its *Senior Pets* client leaflet: the age chart, its weight groups (small up to 20 lb, medium 21–50 lb, large 51–90 lb, giant over 90 lb) and senior ages by size. - Wang T, Ma J, Hogan AN, et al. Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome. *Cell Systems* 2020;11(2):176–185. [doi:10.1016/j.cels.2020.06.006](https://doi.org/10.1016/j.cels.2020.06.006) - Creevy KE, Grady J, Little SE, et al. 2019 AAHA Canine Life Stage Guidelines. *J Am Anim Hosp Assoc* 2019;55(6):267–290. [doi:10.5326/JAAHA-MS-6999](https://doi.org/10.5326/JAAHA-MS-6999) ## More calculators for a good pet day Food, growth, safety and care, for dogs and cats. - [Cat age calculator](https://goodpetday.me/cat-age-calculator/): Your cat's age in human years from the feline vets' chart, with its life stage. - [Pet calorie calculator](https://goodpetday.me/pet-calorie-calculator/): Daily calories for dogs and cats, then grams, cups or cans of your food, split into meals. - [Puppy weight calculator](https://goodpetday.me/puppy-weight-calculator/): An honest estimate of adult weight from today's weight and age, using puppy growth charts. - [Chocolate toxicity calculator](https://goodpetday.me/chocolate-toxicity-calculator/): Dog ate chocolate? Poison line numbers first, then the dose compared with published levels. - [Can my dog eat…?](https://goodpetday.me/can-my-dog-eat/): Common foods marked safe in moderation, caution or toxic, each with the reason. - [Pet sitter care sheet](https://goodpetday.me/pet-sitter-care-sheet/): Feeding, medicines, walks and vet numbers on one printable page for your sitter. - [Pet name generator](https://goodpetday.me/pet-name-generator/): Hundreds of names by theme and style, with a favourites list that stays on your device. ## Recommended Two free services that help with the online side of pet life. Disposable email · no sign-up ### CleanTempMail Pet shops, food brands and breeders all want your email address in return for coupons, free samples or a puppy-pack voucher. CleanTempMail gives you a free temporary inbox straight away, with no sign-up, a random or custom address on hundreds of domains, and messages deleted automatically after 3 days. Grab the offer; your real inbox stays quiet. [Get a temporary inbox](https://cleantempmail.com/) Disposable cloud browser · free domain lookups ### WebTraceCheck Thinking of buying a puppy, or a bargain on supplies, from a website you have never heard of? WebTraceCheck's free DNS and domain lookup shows the details behind a site's domain, and its disposable cloud browser opens unfamiliar links on an isolated desktop that is deleted after each session. Nothing to install, with free time every day. [Try WebTraceCheck](https://webtracecheck.com/) ## Questions **Is one dog year really seven human years?** No. The AVMA says plainly that dogs do not age seven human years for each dog year. Most of the growing up happens early: by the size chart a 1-year-old dog is about 15 in human years and a 2-year-old about 24. After that the pace depends on size, with big dogs ageing faster. **Which size should I pick for a mixed-breed dog?** Go by the weight your dog is, or is expected to be, as a healthy adult. If your dog sits between two sizes, try both: up to about age 6 the chart gives almost the same answer for small and medium dogs, and the gap only widens in later years. **Why is the DNA number so much higher for young dogs?** The formula uses a logarithm, which climbs steeply at first and then flattens. The study found that the DNA marks in dogs change fastest in the first year or two, so a young adult dog lines up with a person in their thirties. By old age the formula gives lower numbers than the chart, because its curve has flattened. **Does this work for puppies?** For the life stage, yes. The size chart starts at 1 year (about 15 human years), so younger puppies show as under 15. We show the DNA formula from age 1 too: below that its curve drops so steeply that it reaches zero at about 7½ weeks, which is not a useful comparison.