How many years is 13 dog years? How many human years is 13 dog years?

Dogs age much faster than humans, so dogs are usually adults after 2 years.

It is not a straight linear relationship. Instead, a dog might age 15 human years
during its first year, and only about 4 human years/year after age two or three.

In general, big dogs have shorter life spans than smaller dogs.

Note that this is just an approximation.