How dog years really work
Dogs mature quickly in their first two years. A widely used approximation gives the first year about 15 human years and the second year another 9, putting a two-year-old dog at roughly 24 human years regardless of size.
After that, the conversion depends on size. Small breeds add about four human years per dog year, medium breeds five, large breeds six and giant breeds around seven. If your dog is a mixed breed, choose the size range they are expected to reach as an adult.
Why the 7-year rule is misleading
Multiplying by seven assumes dogs age at a constant rate, which they do not. It overstates how old a young dog is and understates the last part of a large dog’s life. A one-year-old dog is sexually and physically mature, closer to a teenager than a seven-year-old child.
Size matters because large and giant breeds age faster and often have shorter lifespans. A seven-year-old Great Dane is already a senior, while many seven-year-old small breeds are still active adults.
What the life stage means for care
Puppies need vaccines, parasite prevention and socialisation. Adults benefit from an annual exam and dental checks. Once your dog reaches senior status for their size, ask your vet about annual bloodwork and blood pressure checks, which catch kidney, thyroid and heart problems earlier.
- Small breeds: senior from about 10 years.
- Medium breeds: senior from about 9 years.
- Large breeds: senior from about 8 years.
- Giant breeds: senior from about 7 years.