How to Calculate a Dog’s Age

The old formula for obtaining the age of your dog is to multiply every year of a dog’s life by seven human years. But that’s not accurate. A dog is full grown at twelve months which would be age eighteen in human terms. From this point on, to calculate the true age of your dog, figure that every dog year is the equivalent of five human years.
Thus a ten-year old dog is sixty-three years of age in human terms calculated this way. The first year of a dog’s life counts as eighteen; then add five years for every additional year. Since there are nine additional years, add forty-five to the eighteen to arrive at sixty-three. This holds true for an average fifty pound dog.

For larger breeds the first year holds true but add as much as eight years for each additional year. So a ten-year old larger dog would be more like ninety-years old. And for smaller breeds add four years for each additional year. So a ten-year old smaller dog would be more like fifty-four years old.