Dog Age Calculator
Convert your dog's age into human years.
Human age equivalent
39years
- Dog's age
- 5 years
Approximate — breeds age at different rates.
v1.0 · Reviewed September 2026
How this is worked out
The first year counts as 15 human years and the second as 9 more. Each year after that adds 4 for a small dog, 5 for a medium dog and 6 for a large one.
Worked example
- 5 years old
- Medium size
24 for the first two years, plus 3 × 5
39 human years
Assumptions and limits
- A widely used approximation, not a biological measurement. The old rule of seven years per year is less accurate than this staged version.
- Larger breeds age faster and have shorter lifespans, which is why the size option changes the later years.
- Health, diet and individual variation matter more than any formula.