Convert your dog's age to human years using breed-size adjusted formulas — far more accurate than the old "multiply by 7" rule.
Dogs age rapidly in their first two years, then more slowly. A 1-year-old dog is roughly equivalent to a 15-year-old human. By age 2, they're around 24. After that, each dog year equals roughly 4–5 human years depending on breed size. Large and giant breeds age faster and have shorter lifespans than small breeds.