The 7-year myth
The popular “1 dog year = 7 human years” rule comes from rough lifespan averages — not biology. Dogs don’t age linearly.
The real formula
Year 1 ≈ 15 human years. Year 2 adds 9. After that, small breeds age ~4 years/year, medium ~5, large ~6, giant ~7. Our Dog Age Calculator uses this veterinary framework.
Why bigger dogs age faster
Researchers think it’s tied to faster cell division and shorter telomere length in large breeds. A Great Dane at 6 is biologically similar to a Chihuahua at 10.
When to call your dog “senior”
Small breeds: 10–11. Medium: 8–9. Large: 7–8. Giant: 5–6. Senior care — joint support, slower food, more vet visits — should start then.
