Dog Age Calculator

A dog's first year is roughly equal to 15 human years, and the second year adds about 9 more, so a 2-year-old dog is a young adult of around 24. After that, the pace depends on size. Small dogs add about 4 human years for every birthday, while giant breeds can add 7 or more.

That is why a 10-year-old Chihuahua and a 10-year-old Great Dane are at very different stages of life: the Chihuahua is about 56 in human years, and the Great Dane is closer to 79. Use the calculator above for your own dog, or find their age in the chart below.

The idea that one dog year equals seven human years is easy to remember, but it does not match how dogs actually grow up. By the 7 year rule, a 1-year-old dog would be like a 7-year-old child. In reality, most 1-year-old dogs are close to fully grown and can have puppies of their own, which is much more like a teenager.

The rule goes wrong in two ways:

• It is far too slow at the start. Dogs race through puppyhood and adolescence in their first two years.
• It ignores size. After about age 5, small dogs age more slowly than the rule suggests, and large and giant dogs age faster.

No one is quite sure where the 7 year rule came from. It was probably just a simple way of comparing an average dog lifespan with an average human one.

Across most of the animal world, bigger species tend to live longer: elephants outlive mice. Dogs are a surprising exception. Within dogs, the bigger the breed, the shorter the typical lifespan.

Researchers think large and giant breeds grow so fast that their bodies age faster once they are adults. They also tend to develop age-related problems, like joint disease and some cancers, at younger ages. Typical lifespans look like this:

• Small dogs (20 lb or less): about 12 to 16 years
• Medium dogs (21 to 50 lb): about 10 to 14 years
• Large dogs (51 to 90 lb): about 10 to 12 years
• Giant dogs (Over 90 lb): about 7 to 10 years

Breed matters too. Some breeds have specific health concerns, and flat-faced breeds can face extra challenges. But genetics are only part of the story. Keeping your dog at a healthy weight, staying active, caring for their teeth, and seeing the vet regularly can all add healthy years. See how long dogs live for life expectancy by breed.