Dog Age Calculator
How old is your dog in human years? Enter your dog's age and size to see two answers: the 2019 research formula based on the natural log of age, and the classic chart that depends on the size of the dog. It runs in your browser.
Runs in your browser. Your files are never uploaded.
Loading Dog Age Calculator…
How to use Dog Age Calculator
- Enter your dog's age in years and months.
- Choose the size: small, medium, large or giant.
- Read the human-equivalent age from the research formula.
- Compare it with the classic size-based chart result.
The research formula
Human age is estimated as 16 x ln(dog age in years) + 31. It rises quickly in early life and slows down later. The formula starts to make sense around age 1, so for younger dogs this tool shows a simple linear estimate instead.
The classic size chart
- The first dog year counts as about 15 human years.
- The second year adds 9, reaching about 24.
- After that, each year adds 4 for small dogs, 5 for medium, 6 for large and 7 for giant dogs.
Why the answers differ
The two methods come from different ideas, so they will not match exactly. The formula ignores size, while the chart ignores biology. Use both as a rough guide and pay more attention to your dog's health and behaviour.
Limits
These are estimates for fun and a rough guide, not veterinary advice. Breed, genetics and health change how dogs age. Ask your vet about care for your dog's age. Calculation happens in your browser and nothing is uploaded.
Why use this dog age calculator tool
- Two methods. See the 2019 formula and the classic size chart side by side.
- Size matters. The chart ages large and giant dogs faster than small ones after the second year.
- Puppies handled. Under 1 year the formula does not apply, so a simple straight-line estimate is shown with a note.
- Private and free. Everything is calculated in your browser. Nothing is uploaded, and there is no account or sign-up.
Frequently asked questions
How do I convert dog years to human years?
The old rule of multiplying by 7 is too simple. This tool uses a research formula, 16 times the natural log of the dog's age plus 31, and a chart that counts about 15 for year one and 9 more for year two, then adds more per year by size.
Is a dog year really 7 human years?
No. Dogs age fastest in their first two years, then more slowly, and the pace depends on size. A 7-times rule overstates the age of young dogs and misjudges older ones. Both methods here are more realistic.
What is the 2019 dog age formula?
Researchers studying changes in DNA methylation proposed that human age is about 16 times the natural logarithm of the dog's age in years, plus 31. It was developed from Labrador retrievers and is mostly valid from about 1 year of age.
Why does size change the result?
Larger dogs tend to have shorter lives and are often considered senior sooner. The size chart adds 4, 5, 6 or 7 human years per dog year after the second year for small, medium, large and giant dogs.
Is anything stored or sent?
No. The calculation is done in your browser, and nothing is uploaded or saved.
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