How it works
The old 'multiply by seven' rule isn't accurate. Dogs mature very quickly: a one-year-old dog is roughly comparable to a 15-year-old person, and a two-year-old to about 24.
After that, each year adds roughly 4–7 human years depending on size, because larger breeds age faster. This is a rough comparison, not a medical age.
Many dogs benefit from senior check-ups from middle age — earlier for giant breeds. Ask your vet when to start for your dog.
Quick reference
| Dog's age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 |
| 4 years | 32 | 34 | 36 | 38 |
| 6 years | 40 | 44 | 48 | 52 |
| 8 years | 48 | 54 | 60 | 66 |
| 10 years | 56 | 64 | 72 | 80 |
| 12 years | 64 | 74 | 84 | 94 |
Approximate human-year equivalents by dog size.
Questions
Is one dog year seven human years?
Not really. Dogs age fastest in their first two years — a one-year-old is roughly like a 15-year-old — and then more slowly, at a rate that depends on size.
Why do big dogs age faster?
Larger breeds tend to have shorter lifespans, so after the first two years each year counts for more human years than it does for small dogs.
When is a dog a senior?
It varies by size; giant breeds can be considered senior from around 5–6, small breeds later. Your vet can advise when to start senior check-ups.
General guidance for healthy pets, not veterinary advice. Needs vary — your vet can advise for your pet.