Is a 7-year-old dog really 49? Not quite. Dogs grow up fast in their first two years, then age at a pace that depends on their size, so the old “multiply by 7” rule is off at both ends. Enter your dog’s age in years and months, or switch to Birthday and pick the date. Then choose your dog’s adult size. For a puppy or a mixed breed, go by the weight you expect when fully grown. You get the age in human years, the life stage, what the ×7 rule and a DNA-based formula would say, and a dog age chart for every size.
How it works: the calculator uses the size-based dog age chart that follows American Veterinary Medical Association (AVMA) guidance. A dog’s first year equals about 15 human years and the second adds about 9 more. Small, medium and large dogs then add about 4 a year up to age 5. After that, small dogs keep adding about 4 a year, medium dogs 4–5 and large dogs 5–6. Giant dogs start at 12, add about 10 in year two and then about 7 a year. Ages between birthdays are filled in proportionally, and ages past 16 continue at the last yearly rate. The DNA-based formula, human age = 16 × ln(dog age) + 31, comes from a 2020 UC San Diego study of Labrador Retrievers, so it fits other breeds less well. Life stages loosely follow the AAHA guidelines: puppy while still growing fast (up to about 9 months, longer for big breeds), young adult to about 3, mature adult after that, and senior for roughly the last quarter of a typical lifespan for the size.