How to use the Dog & Cat Age Calculator
- Choose dog or cat.
- Enter your pet’s age and, for dogs, their size.
- See the equivalent human age and life stage.
- Optional: compare the size assumptions for the same dog age.
The “multiply by 7” myth
Dogs mature much faster than people in their first two years: a 1-year-old dog is roughly like a 15-year-old human. After that, aging slows — and large breeds age faster than small ones. That is why a single multiplier is inaccurate.
How we calculate it
For dogs we use the widely cited veterinary approach: 15 human years for year one, 9 more for year two, then 4–7 years per year depending on size. We also show the 2019 DNA methylation formula from UC San Diego: human age = 16 × ln(dog age) + 31. For cats: 15 for year one, 24 at two, then 4 per year.
Frequently asked questions
How old is a 10-year-old dog in human years?
About 56 for a small dog, 60 for a medium dog and 66–78 for large and giant breeds.
How long do cats live?
Indoor cats commonly live 12–18 years, and many reach their 20s.