How it works
This uses a popular approximation: the first year counts as 15 human years, the second adds 9 (24 total), and each year after adds 4 for small dogs, 5 for medium dogs, and 6 for large dogs. So a 5-year-old medium dog is 24 + 3×5 = 39. This is a rough guide — real ageing varies by breed, health and lifestyle, and it is not veterinary advice.
Frequently asked questions
Is the old 7-years-per-year rule right?
No — dogs age fastest in their first two years, then slow down, so a flat multiplier is misleading.
Does size really matter?
Yes, in general larger dogs tend to age faster in later life, which is why this approximation adds more per year for large dogs.