CNN How do you compare a dog's age to that of a person? A popular method says you should multiply the dog's age by 7 to compute how old Fido is in "human years." And that's because the scientists behind a new study say dogs and humans don't age at the same rate. Based on the study, a one-year-old dog compares to a 30-year-old human, a four-year-old dog to a 52-year-old human. A graphic in the study makes the age comparisons intuitive and provides some helpful context for dog owners, including the scientists themselves.