Dog Age Calculator
Convert your dog's age to human years by breed size. The modern formula accounts for how dogs age faster when young.
years
Human Equivalent Age
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Life Stage —
Expected Lifespan —
How to Use This Calculator
- Enter your dog's age in years.
- Select your dog's Breed Size — larger breeds age faster.
- The calculator shows the human equivalent age, life stage, and expected lifespan.
Formula
Dog aging rates (human years per dog year by year):
- Year 1: ~15 human years
- Year 2: ~9 human years
- Year 3+: 4–8 human years depending on size
Example
A 5-year-old medium-sized dog.
- Year 1: 15, Year 2: +9, Year 3: +5, Year 4: +5, Year 5: +5
- Human Age = 39 years
- Life Stage: Adult
Frequently Asked Questions
- Not quite. Research shows dogs age rapidly in their first two years — a 2-year-old dog is more like a 25-year-old human — then aging slows. The rate also depends on breed size.
- Smaller dog breeds tend to age more slowly than large or giant breeds. Giant breeds like Great Danes may be considered senior at age 5, while small dogs may not be senior until 10.
- A 2020 study in Cell Systems used DNA methylation patterns to map dog aging. This calculator uses an approximation based on breed size and known aging rate milestones.
- Life stages vary by breed size. This calculator estimates whether your dog is a Puppy, Adolescent, Adult, Mature Adult, or Senior based on their age relative to expected lifespan.