How the calculation works
Researchers compared DNA methylation in dogs and people and fitted a curve: human age = 16 × ln(dog age) + 31 [1]. A 1-year-old dog maps to about 31, a 4-year-old to about 53, and a 10-year-old to about 68. The curve rises fast in youth and flattens later, which matches how quickly puppies mature.
Limits you should know
- The formula was built from Labrador Retrievers [1]; small and giant breeds may age differently.
- It is only meaningful for dogs 1 year and older, so puppies get the life-stage view.
- Size changes when a dog becomes “senior”: about 8–11 years for small breeds, 8–10 for medium, 8–9 for large and 6–7 for giant breeds, per the AVMA [2].
The AVMA notes that dogs do not age at a rate of 7 human years per dog year [2], and recommends veterinary visits twice a year or more for senior pets.