There is no simple equation that will convert dog years into human years. Many people believe that a dog ages seven years for every one human year, but this is just a myth.
Researchers believe that in their first year of life, the amount dogs age is comparable to 15 years for humans. After that, the dog-year-to-human-year ratio begins to taper off. The adjusted ratio can be anywhere from five to ten dog years for every human year depending on whether the dog is a large or small breed. Large breeds generally take longer to reach sexual maturity than small breeds, and smaller breeds tend to have significantly longer life spans.