How dog years work
Veterinary guidance commonly counts a dog's first year as about 15 human years and the second as about 9 more. After that, each year adds roughly 4 to 7 human years depending on size, because big dogs have shorter lifespans. Published charts differ by a year or two, so treat these as approximate.
| Dog's 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 |
| 8 | 48 | 54 | 60 | 66 |
| 10 | 56 | 64 | 72 | 80 |
| 12 | 64 | 74 | 84 | 94 |
| 14 | 72 | 84 | 96 | 108 |
| 16 | 80 | 94 | 108 | 122 |
The DNA-based formula
A 2020 study in Cell Systems compared DNA changes in Labrador retrievers and people and proposed a different formula. It ages young dogs even faster: a 1-year-old dog is like a 31-year-old human.
It was built from one breed, so treat it as an interesting comparison rather than a rule.
Frequently asked questions
When is a dog a senior?
Small dogs are often considered seniors around 10 to 12, medium dogs around 8 to 10, and large and giant breeds as early as 6 to 8.
Is one dog year really seven human years?
Not exactly. That rule averages a dog's lifespan against a human's, but it misses how fast dogs mature early and how size affects aging.