Dog Age in Human Years
Convert your dog's age into human years two different ways — the epigenetic DNA-methylation formula and a size-adjusted veterinary chart — then see the matching life stage. Cats are covered too.
Your pet
The two methods disagree on purpose. The logarithmic formula follows a molecular ageing clock that sprints through the first year and then slows down; the size-adjusted chart follows the practical veterinary timeline of puppy, adult and senior. Both are estimates — a checkup beats any calculator.
How to use this calculator
1. Pick the species
Dogs and cats age on completely different schedules, so start with the toggle. Cats follow a single curve regardless of breed; dogs need one more piece of information, which is body size.
2. Choose the adult size class
Enter the weight your dog reaches at full growth, not their weight today — a four-month-old Labrador puppy is a large-breed dog even at 25 lb. Size is the single biggest driver of how fast a dog ages after adolescence.
3. Enter years and extra months
Months are worth adding for anything under about two years old. A three-month-old puppy and a ten-month-old puppy are worlds apart developmentally, and rounding both to “under one year” hides that.
4. Read both numbers, not just one
Treat the headline chart figure as the everyday answer — it is what a vet means by adult or senior. Treat the epigenetic figure as the biological view of how far along the molecular clock has run. The explore panel shows the full curve for all four size classes so you can see where your dog sits.
About dog and cat age conversion
Is one dog year really seven human years?
No. The multiply-by-seven rule is a myth with no basis in biology. Dogs do most of their growing up in the first two years, so a one-year-old dog is closer to a human teenager than to a seven-year-old child. The rule also ignores body size entirely, even though a Great Dane and a Chihuahua age at very different speeds. Every method on this page beats multiplying by seven.
Where does the 16 × ln(age) + 31 formula come from?
It comes from research on DNA methylation, the chemical marks that accumulate on DNA as an animal ages. Researchers compared methylation patterns in Labrador Retrievers with patterns in humans and fitted a logarithmic curve between the two epigenetic clocks. Because the study centred on a single breed, the formula does not adjust for body size and it is only meaningful from roughly one year of age onward.
Why do the two methods give different numbers?
They measure different things. The logarithmic formula tracks a molecular ageing clock, which runs extremely fast in the first year and then slows down sharply, so it produces high numbers for young adult dogs. The size-adjusted chart is a practical veterinary rule of thumb built around life expectancy and life stage. Use the chart for everyday questions such as when a dog counts as senior, and treat the formula as the biological view.