There is a widely-held notion that one year of a dog’s life is equivalent to seven years of a human’s. But the calculation to determine a dog’s age is more complicated. Breed, size, health and other facets ultimately determine how long a dog will live. Most people, however, realize that large-breed dogs do not live as long as smaller ones. As a rough guideline, the following chart is useful:
Thus a one-year-old dog is like a teenage person, and a two-year old is like a 24-year-old human. Each additional year following is equivalent to five human years.
The oldest dog on record was an Australian cattle dog named Bluey, who lived to be more than 29 years old. That’s equivalent to more than 160 in human years!
I have sometimes thought of the final cause of dogs having such short lives and I am quite satisfied it is in compassion to the human race; for if we suffer so much in losing a dog after an acquaintance of ten or twelve years, what would it be if they were to live double that time? Sir Walter Scott
To get a more accurate estimate of your dog’s age: http://pets.webmd.com/dogs/how-to-calculate-your-dogs-age (PEDIGREE®)