How it's calculated
The AVMA's guideline for a medium dog: the first year equals about 15 human years, the second adds about 9, and each year after adds about 5. Size matters after age 2. Small dogs add about 4 human years a year and large and giant breeds 6-7, because bigger dogs age faster and live shorter lives.
The second number comes from a 2020 study of DNA methylation in Labrador retrievers: human age = 16 × ln(dog age) + 31. It ages young dogs very fast, so a 1-year-old comes out at 31.
Dog years to human years chart
| Dog age | Small (under 20 lb) | Medium (20-50 lb) | Large (50-90 lb) | Giant (90+ lb) |
|---|---|---|---|---|
| 1 yr | 15 | 15 | 15 | 15 |
| 2 yr | 24 | 24 | 24 | 24 |
| 3 yr | 28 | 29 | 30 | 31 |
| 4 yr | 32 | 34 | 36 | 38 |
| 5 yr | 36 | 39 | 42 | 45 |
| 6 yr | 40 | 44 | 48 | 52 |
| 7 yr | 44 | 49 | 54 | 59 |
| 8 yr | 48 | 54 | 60 | 66 |
| 9 yr | 52 | 59 | 66 | 73 |
| 10 yr | 56 | 64 | 72 | 80 |
| 12 yr | 64 | 74 | 84 | 94 |
| 14 yr | 72 | 84 | 96 | 108 |
| 16 yr | 80 | 94 | 108 | 122 |
When is a dog a senior?
Roughly: small breeds around 10, medium breeds around 8, large breeds around 7, and giant breeds around 6. Senior dogs benefit from checkups every 6 months, since problems like kidney disease and arthritis are easier to manage when caught early.
Questions
Is one dog year really 7 human years?
No. Dogs grow up much faster than that in the first two years, then age more slowly, and the pace depends on size.
How old is a 10-year-old dog in human years?
About 56 for a small dog, 64 for a medium dog, 72 for a large dog and 80 for a giant breed, using the AVMA-based chart above.
- Chewy, Dog Years to Human Years (AVMA guideline)
- Wang et al., Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome, Cell Systems (2020)
Last reviewed October 20, 2026. Estimates for healthy pets only, not veterinary advice.