With dogs, one-year-equals-seven-human-years is not an unreasonable rule of thumb. But for a cat who lives to 20, that rule makes her age improbably Biblical. A better way to think of a cat’s age is to put it into a category: kitten, junior, prime, and so on. The American Animal Hospital Association agrees, and in conjunction with the American Association of Feline Practitioners has grouped cats’ ages as shown in the table below. This helps the doctor decide what health screenings your pet needs depending on the stage of life she’s in, says Jesse Grady, DVM, a clinical instructor of veterinary medicine at Mississippi State University.