What are dog years?

Dogs age at a quicker rate than humans do. The equivalent of a dog's age in human years largely depends on the size of the dog in question. One dog year can be as much as 15 years in human years.

For dogs of all sizes, including small, medium and large breeds, a dog that is 1 year old has physically matured as much as a human ages in 15 years. The human age equivalent progression is the same for all dog sizes up until a dog reaches 6 years old. Dogs of all sizes that are 5 years old are 36 years old in human years. However, a 6-year-old small dog is equal to 40 in human years, while a large breed, greater than 50 pounds, that is 6 years old is the equivalent of 45 years old in human years.