You might've heard the myth that one regular year is equal to seven dog years, but it's not entirely true. Veterinarian Jesse Grady writes for The Conversation that the logic behind that idea is that, "People observed that with optimal healthcare, an average-sized, medium dog would on average live one-seventh as long as its human owner." The issue here is that not every dog fits this criteria, Grady says dogs and cats age different not just from people but also from each other. This is based partly on breed and characteristics and size. These days, the American Animal Hospital Association has Canine Life Stages Guidelines, which divides dogs into six categories: puppy (0- 0.5 years), junior (0.5- 0.75 years), adult (0.75- 6.5 years), mature (6.5 - 9.75 years), senior (9.75- 13 years) and geriatric (over 13.) Grady says lining up canine and human development milestones over the course of the average life expectancy can help you figure out roughly where in life your animal is. You could also ask your vet, who can let you know about health recommendations that go along with the life stage your pet is in.