How to convert dog years to human years
The old “multiply by seven” rule is a myth. Dogs grow up far faster than people at the start of life, then age at a steadier pace that depends on size. The size-based method used here is a widely used veterinary rule of thumb:
year 1 = 15 human years year 2 = +9 (24 in total) each year after = +4 small · +5 medium · +6 large · +7 giant
The DNA (epigenetic) formula
In 2020, researchers at UC San Diego compared age-related chemical changes to DNA in Labrador retrievers and in humans. They proposed:
human age ≈ 16 × ln(dog age) + 31
It suggests dogs age especially fast early on: a one-year-old maps to about 31 human years. Because it was built on a single breed, we show it alongside the size-based result rather than instead of it.
Dog age chart
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 3 | 28 | 29 | 30 | 31 |
| 4 | 32 | 34 | 36 | 38 |
| 5 | 36 | 39 | 42 | 45 |
| 6 | 40 | 44 | 48 | 52 |
| 7 | 44 | 49 | 54 | 59 |
| 8 | 48 | 54 | 60 | 66 |
| 9 | 52 | 59 | 66 | 73 |
| 10 | 56 | 64 | 72 | 80 |
| 11 | 60 | 69 | 78 | 87 |
| 12 | 64 | 74 | 84 | 94 |
| 13 | 68 | 79 | 90 | 101 |
| 14 | 72 | 84 | 96 | 108 |
| 15 | 76 | 89 | 102 | 115 |
| 16 | 80 | 94 | 108 | 122 |
These figures are estimates for curiosity and general care planning. For health decisions about your dog, talk to your vet.
Frequently asked questions
Is one dog year really seven human years?
No. Dogs mature very quickly, so the first year is roughly 15 human years and the second adds about 9 more. After that, ageing depends on size: small dogs age more slowly than large and giant breeds.
Why do large dogs age faster?
Larger breeds reach maturity on a similar schedule to small ones but have shorter average lifespans, so each adult year counts for more. That is why the calculator asks for your dog’s adult size.
What is the epigenetic (DNA) formula?
A 2020 study by researchers at the University of California San Diego, published in Cell Systems, compared DNA methylation changes in Labrador retrievers and humans. It proposed human age ≈ 16 × ln(dog age) + 31. It was built on one breed, so treat it as an interesting alternative rather than a rule.
When is my dog a senior?
Very roughly, giant breeds can be considered seniors from about 5–6 years, large breeds from about 7, and small and medium dogs from about 8–10. Your vet is the best judge for your individual dog.