Why "multiply by 7" is a myth
The old rule that one dog year equals seven human years is a rough average that fits almost no dog well. Dogs mature very fast in their first two years — a one-year-old dog is roughly a 15-year-old human, and by age two it is around 24 — then age more slowly. Larger breeds also age faster than small ones, so a calculation that ignores size will always be off.
How this calculator works
This tool uses the staged method vets often cite: the first year counts as about 15 human years, the second adds about 9 more, and each year after that adds 4 to 6 human years depending on your dog's size. Smaller dogs add fewer years and tend to live longer; giant breeds add more.
The 2019 science-based estimate
A 2019 study from the University of California, San Diego compared DNA methylation — chemical "ageing marks" on DNA — in Labrador Retrievers and humans, and produced the formula human age = 16 × ln(dog age) + 31. It maps a dog's early rapid ageing surprisingly well, and this calculator shows it alongside the size-based figure so you can compare both.
Frequently asked questions
How old is a 1-year-old dog in human years?
Roughly 15 human years. Dogs reach the equivalent of human adolescence within their first year, which is why the multiply-by-seven rule underestimates young dogs.
Does size really change dog ageing?
Yes. Small dogs often live 14–16 years while giant breeds may reach only 8–10, so larger dogs accumulate more human-equivalent years per calendar year after adulthood.