How old is a four-year-old dog in human years?

A four-year-old dog is roughly equivalent to a 30 to 35-year-old human. Because dogs of different sizes have different lifespans, a small breed such as a toy poodle, Pomeranian, or Bichon is usually about 32 in human years at four, a medium or large breed about 34, and a giant breed already around 35.

Three to four years is the dividing line in a dog’s age. After that, the larger the dog, the faster it ages. By the time a dog is eight, a small breed equals about 48 human years, a medium breed 51, a large breed 55, and a giant breed about 64.