We’ve all heard the phrase “but she’s x in dog years..”. A commonly accepted rule of thumb estimates that one human year equals seven dog years. But what does this calculation really mean? Is it true, and can we estimate how long our dogs will live based on it? Or is it yet another commonly accepted dog myth?
Dog Years to Human Years: Myth vs. Reality
In actuality, the calculation of human years to dog years is less linear than a simple one to seven ratio. In fact, when correlating the life stages, represented by age, of dogs and humans, a key difference is that dogs reach adulthood much faster than humans.
So a more reasonable approximation of the age relationship is that for the first two human years, a dog ages 10-and-a-half dog years. After these first two years, a dog ages about four human years for every dog year.
After these first two years, a dog ages about four human years for every dog year.
Breeds and Dog Years
The calculation of human years to dog years is further complicated by breed. While a smaller dog may live 15 years or longer, a medium to large-sized dog might only live between 10 and 13 years. What’s more, a giant dog such as a mastiff may only have a lifespan of 8 years or so.
Signs of Dog Aging
As with humans, dogs deteriorate both mentally and physically with age. Their ability to hear, see, and move decreases with the years, along with the condition of their skin and joints. In general, their energy level decreases too. It is not uncommon to see dogs graying around the face and beard, and be plagued by diseases common to elderly humans like cancer and arthritis.
The Bottom Line
As a caretaker to an older dog, either as an owner or a dog sitter, the classic equation of one human year to seven dog years can still be important, if not entirely accurate. This rule of thumb can be helpful overall, in other words. For instance, the senior dog you love or care for should be treated as a 70 or 80-year old person would, even though she or he might only be nine or 10 in dog years.