Dog Age Calculator — Dog Years to Human Years by Size
CalculatorA dog age calculator converts dog years to human years using 15 for the first year, +9 for the second, then +4 to +6 per year depending on breed size.
What is it
The old “1 dog year = 7 human years” rule does not match how dogs mature. Dogs age quickly in their first two years — a 2-year-old dog is roughly a 24-year-old human — and then add about 4 human years per year for small breeds, 5 for medium, and 6 for large. A 2020 UCSD study of Labrador DNA methylation proposed human age = 16 × ln(dog age) + 31, which captures fast early aging; the tool shows this value for reference.
How to use
- 1Select the breed size (small, medium, or large).
- 2Enter the dog’s age in years.
- 3Check the human-age estimate and the logarithmic reference value.
Reference
| Dog age | Small | Medium | Large |
|---|---|---|---|
| 1 yr | 15 | 15 | 15 |
| 3 yr | 28 | 29 | 30 |
| 7 yr | 44 | 49 | 54 |
| 10 yr | 56 | 64 | 72 |
| 15 yr | 76 | 89 | 102 |
Sources & standards
- Quantitative translation of dog-to-human aging (epigenetic clock) - Cell Systems (Wang et al., 2020)
- How to calculate dog years to human years - American Kennel Club
FAQ
How old is a 5-year-old medium dog in human years?
About 39: 24 for the first two years plus 3 × 5. A small dog would be about 36 and a large dog about 42.
Is the “1 dog year = 7 human years” rule accurate?
No. Dogs mature fast in the first two years and age at different rates by size, so vets prefer the 15 + 9 + size-based chart or the DNA-based logarithmic formula.
Is dog age calculator input sent to a server?
No. This tool runs in your browser and does not send input to a server.