Dog Age Calculator (Dog Years to Human Years)

The old multiply-by-7 rule is a myth: dogs age fastest in their first two years and then slow down, and how much they slow down depends on their adult size. This calculator shows two published estimates side by side. The first is the size-class table popularized by the American Veterinary Medical Association and the American Kennel Club: the first year of a dog's life counts as about 15 human years, the second adds 9 more, and every year after that adds 4 (small dogs under 10 kg), 4.5 (medium, 10–25 kg), 5 (large, 25–45 kg) or 6 (giant, over 45 kg).

The second estimate comes from a 2019 University of California San Diego study that compared DNA methylation patterns — chemical marks that accumulate with age — in dogs and humans. The resulting formula, human age = 16 × ln(dog age) + 31, was derived from Labrador Retrievers and is defined for dogs aged one year and up. It paints a different picture from the table: a 1-year-old dog is already about 31 in human terms, a 4-year-old about 53, and the curve then flattens dramatically.

Neither model is 'the truth' — they answer slightly different questions. The size table tracks practical life expectancy: giant breeds really do become seniors around age 6–7 while small breeds often stay spry into their teens. The epigenetic clock tracks measurable molecular aging, which is front-loaded into the first years of life. This tool shows both, labels their sources, and adds a life-stage estimate (puppy, young adult, mature adult, senior) with the senior threshold adjusted for your dog's size class.

Everything is computed instantly in your browser — no sign-up, and nothing you enter is uploaded anywhere. The result is an estimate for healthy dogs, not a veterinary assessment: breed, weight, diet and preventive care all shift individual aging, so use the numbers as context for care decisions, not as a diagnosis.