Dog Age Calculator: Dog Years to Human Years

The first year counts for about 15 human years and the second brings the total to about 24. From year three onward the rate depends on breed size: on average a small dog adds about 4 human years per calendar year, a medium dog about 5, a large dog about 5 to 6, and a giant breed about 7. So a 5-year-old medium dog is about 36 in human years.

No. The 7-year rule is a myth. Dogs age much faster in their first two years, roughly 15 human years in year one alone, and after that the rate depends heavily on breed size. Small dogs age more slowly than the rule suggests, while giant breeds age faster.

It depends on size. Using the AKC chart, a 10-year-old dog is about 56 in human years if it is small, 60 if medium, 66 if large, and 79 if it is a giant breed. That 23-year spread is why any single dog years to human years number without a size attached is unreliable.

Larger dogs age faster than smaller dogs after the first two years. A Great Dane at 8 years old is roughly equivalent to a 64-year-old human, while a Chihuahua at 8 is only about 48. Giant breeds also start slightly behind in year one, then overtake every other size by about age 3.

The most accurate published formula uses the natural logarithm: human age is roughly 16 multiplied by ln(dog age in years), plus 31. It comes from a 2020 study of DNA methylation in Labrador Retrievers. It is a single-breed model though, so the size-adjusted AKC chart used here remains the more practical answer for a dog of any size.

Small dogs are generally considered senior at about 10 years, medium dogs at 9, large dogs at 8, and giant breeds as early as 6. Senior status tracks size because larger dogs have shorter lifespans, and it is the point at which most vets recommend twice-yearly exams and bloodwork.

No, cats follow a different curve and size barely matters for them. A 1-year-old cat is about 15 in human years, a 2-year-old is about 24, and each year after adds about 4 regardless of breed. Use the Cat Age Calculator for cats.