Convert dog years using the modern log formula.
Dog age in human years depends on size and breed, but a simple approximation: first year = 15 human, second = 9 more, then 4–5 per year after.
Small dogs age slower than large dogs after middle age.
Veterinary science has moved away from the old flat '×7' rule toward this front-loaded model because dogs mature to adulthood in just one to two years — the early years pack in far more biological aging than a simple multiplier would suggest.
5-year-old dog ≈ 15 + 9 + 3×5 = 57 human years (rough small/medium approximation).
No — it's a shortcut that overstates in the first two years and understates in old age. Puppy year one is closer to 15.
Yes — great danes and other giant breeds age faster; tiny breeds like chihuahuas live longer.
This varies by size — large breeds are often considered senior around 6-7 years old, while small breeds may not reach that stage until 10 or later, reflecting their generally longer lifespans.