Dog age calculator: dog years to human years

The old "multiply by 7" rule is wrong — dogs age fast as puppies and slower as adults, and big dogs age faster than small ones. Enter your dog's age and size for the real answer, using the veterinary size chart plus the newer science formula.

Dog age chart (dog years to human years)

How many dog years are in 1 human year?

There is no single number — that's why the "1 to 7" rule fails. A dog's first year equals about 15 human years, the second adds roughly 9 more (24 total), and after that each year adds 4–8 human years depending on size: about +4–5 for small dogs, +5–6 for medium, +6–7 for large, and +7–8 for giant breeds.

How old is a 5-year-old dog in human years?

36 to 45 human years, depending on size: 36 for a small dog, 37 for a medium dog, 40 for a large dog, and 45 for a giant breed. Try it in the calculator above with your own dog.

The science formula (UC San Diego)

In 2019, researchers at UC San Diego studied DNA methylation in Labrador retrievers and published a formula that tracks aging far better than the classic chart: human age = 16 × ln(dog age) + 31. By that formula, a 1-year-old dog is like a 31-year-old human, a 2-year-old like a 42-year-old, and an 8-year-old like a 64-year-old. Our calculator shows both results so you can compare.

Life stages: is your dog a senior?

Dogs are considered seniors in the last 25% of their expected lifespan — around age 7 for giant breeds, 8–9 for large dogs, 10 for medium, and 11–12 for small dogs. Senior dogs benefit from twice-yearly vet visits and a watchful eye on food and weight. Speaking of food: check anything new against our list of what human foods dogs can eat, and never share the chocolate.