Dog Age Calculator: Dog Years to Human Years by Size
Multiply by 7 is wrong. See how old your dog really is in human years, by size, with two vet-cited methods and their current life stage.
About – human years (size-based chart)
Epigenetic-clock estimate: –
Life stage: –
How the two methods work
The size-based chart follows the pattern published by the AVMA and the AAHA Canine Life Stage Guidelines: a dog's first year is worth about 15 human years, the second year adds about 9 more (24 total by age 2), and after that each extra dog year adds a fixed number of human years that grows with adult size — 4 for small dogs, 5 for medium, 6 for large, 7 for giant breeds.
The epigenetic-clock formula comes from Wang et al. (2020, Cell Systems), who compared DNA methylation patterns in dogs and humans: human_age = 16 × ln(dog_age) + 31. Because it is built on a logarithmic model of methylation drift, it is only meaningful once a dog is past its fastest year of development, so this calculator shows it only for dogs 1 year and older.
Size-based human-age chart
| Dog age | Small (≤20 lb) | Medium (21–50 lb) | Large (51–90 lb) | Giant (>90 lb) |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 |
| 3 years | 28 | 29 | 30 | 31 |
| 5 years | 36 | 39 | 42 | 45 |
| 7 years | 44 | 49 | 54 | 59 |
| 10 years | 56 | 64 | 72 | 80 |
| 13 years | 68 | 79 | 90 | 101 |
| 15 years | 76 | 89 | 102 | 115 |
Why "×7" is wrong
The old rule of thumb — multiply a dog's age by 7 — assumes dogs age at a constant rate that is identical for every breed and every year of life. Neither is true. A one-year-old dog is already close to physically mature, not "7 years old"; a lot of aging happens in the first two years and then slows down. Size matters too: small dogs tend to live proportionally longer than giant breeds, so a flat multiplier overstates a small dog's age and understates a giant breed's. Both the AVMA and the AAHA guidelines linked below explicitly move away from the ×7 rule in favor of a size-adjusted chart.
Life stages
Life stage boundaries are approximate and size-adjusted, following the general pattern in the 2019 AAHA Canine Life Stage Guidelines — exact months vary by breed, not just weight class.
| Stage | Small / medium dogs | Large / giant dogs |
|---|---|---|
| Puppy | Birth to about 1 year | Birth to about 1.5–2 years |
| Young adult | About 1–6 years | About 1.5–4 years |
| Mature adult | About 6–9/10 years | About 4–6/8 years |
| Senior | About 9/10–13/14 years | About 6/8–9/11 years |
| End of life | 13/14+ years | 9/11+ years |
Limitations
- Both methods are population averages. Breed, individual health, spay/neuter status and genetics all shift the real number.
- The epigenetic-clock formula is based on Labrador retrievers in the original study; it is a useful second opinion, not a diagnosis.
- Life stage boundaries are approximate — ask your vet for guidance specific to your dog's breed and health history.
Sources
- How to Convert Dog Years to Human Years — American Veterinary Medical Association (AVMA) (September 23, 2026)
- 2019 AAHA Canine Life Stage Guidelines — American Animal Hospital Association (AAHA) (September 23, 2026)
- Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome — Cell Systems (Wang, Ma, Wang, Sale, Wang et al., 2020) (September 23, 2026)