Dog Age Calculator
Find out how old your dog is in human years. Enter your dog's age and size, since big dogs age faster than small ones after the first two years.
Age in human years
44 years
Check the highlighted field to see your result.
- Size group
- Medium
- Each year now adds
- 5 years
Results are estimates for information only and do not constitute financial, medical, or legal advice.
How dog years are counted
A dog's first year is roughly 15 human years and the second adds about 9 more. After that, each year adds 4 human years for small dogs, 5 for medium dogs, 6 for large dogs, and 7 for giant dogs. It's a widely used size-based chart, not the result of a single scientific study; breed, health, and lifestyle also matter.
Dog life stages
The 2019 AAHA Canine Life Stage Guidelines don't set exact ages for every stage, since they depend on size and breed: puppy until rapid growth stops (about 6 to 9 months), young adult until fully mature (usually by 3 or 4 years), then mature adult, and senior during the last 25% of the breed's expected lifespan.
The formula
Human years = 24 + (dog age − 2) × years per size
Worked example
Your medium-sized dog is 6 years old.
- First two years: 15 + 9 = 24 human years.
- The other 4 years: 4 × 5 = 20 human years.
- Total: 24 + 20 = 44 human years.
Frequently asked questions
Is one dog year really seven human years?
No, that's a myth. Dogs grow up much faster in their first two years, and after that the pace depends on their size. A 1-year-old dog is more like a 15-year-old person.
Why do big dogs age faster?
Large and giant breeds tend to have shorter lives than small breeds, so after the first two years each year counts for more human years.
Is there a more scientific formula?
A 2020 study based on DNA changes in Labrador retrievers proposed human age ≈ 16 × ln(dog age) + 31. It fits that breed well but wasn't designed for every size, so this calculator uses a size-based chart.