Dog Age Calculator

Dog years to human years chart

Find your dog’s age on the left and its adult size at the top. The first four columns are the American Kennel Club chart, based on guidance from the American Veterinary Medical Association; the last column is the DNA clock from UC San Diego. Small dogs are 20 lb (9 kg) or less as adults, medium 21–50 lb (10–23 kg), large 51–100 lb (23–45 kg) and giant over 100 lb (45 kg).

How to calculate dog years

The size chart. A dog’s first year equals about 15 human years and the second adds about 9, so a 2-year-old dog is around 24. After that every year adds about 4 to 5 human years for small and medium dogs, about 5 to 6 for large dogs and about 7 for giant breeds, because big dogs age faster. For puppies under one year the calculator scales the first year evenly, which is only a rough guide.

The DNA clock. In 2020 scientists at the University of California San Diego compared chemical marks on the DNA of Labrador Retrievers and people and published a formula: human age = 16 × ln(dog age) + 31. It says dogs age very fast when young: a 1-year-old Lab is like a 31-year-old person, a 4-year-old like 53. It was built on one breed, so we show it next to the size chart rather than instead of it.

Why not times seven? The old rule makes a 1-year-old dog seven, when most dogs can already have puppies at that age, and it makes a 15-year-old Chihuahua and a 15-year-old Great Dane the same age, when few Great Danes ever reach 15.

Dog life stages

The American Animal Hospital Association’s 2019 Canine Life Stage Guidelines describe four stages before the end of life:

• Puppy: from birth until rapid growth stops, around 6 to 9 months depending on size.
• Young adult: until the dog is fully mature in body and behavior, by 3 to 4 years in most dogs.
• Mature adult: from then until the last 25% of the dog’s expected lifespan.
• Senior: the last 25% of the expected lifespan.

That is why the calculator asks for the breed: the senior years start when three quarters of that breed’s typical life have passed, not at one age for every dog.

How long do dogs live? Lifespan by breed

Median lifespans from the largest study of its kind, 584,734 dogs in the United Kingdom (McMillan et al., Scientific Reports, 2024): half of the dogs of a breed lived longer, half shorter. Mixed-breed dogs lived a median of 12 years. The last column shows when a typical dog of the breed becomes a senior. Weights are typical adult weights.

Caring for your dog at every age

Puppies outgrow collars and harnesses within weeks, so measure often; our puppy growth calculator predicts the adult size and the harness size calculator finds the size that fits today. Adult dogs do best with daily exercise and a steady weight. Senior dogs feel the cold sooner, sleep more and can slip on smooth floors: a warm dog sweater, a soft bed from our designer dog beds and non-slip dog shoes help, and the how cold is too cold calculator tells you when to keep walks short. Ask your vet how often an older dog should come in for a check-up.

Dog age calculator FAQ

How old is a 1-year-old dog in human years?

About 15 human years on the size chart for small, medium and large dogs (12 for giant breeds). On the DNA clock from UC San Diego a 1-year-old dog is about 31, closer to a young adult. Either way, the first year is when dogs age fastest.

Is 1 dog year equal to 7 human years?

No. The 7-year rule is a myth: dogs grow up far faster in the first two years (about 24 human years by age 2) and then age more slowly, and big dogs age faster than small ones.

How old is a 10-year-old dog in human years?

On the AKC size chart a 10-year-old dog is 56 human years if it is small, 60 if medium, 66 if large and 79 if giant.

At what age is a dog a senior?

Vets’ AAHA guidelines call a dog senior in the last quarter of its expected lifespan. With the median lifespans from a study of 584,734 dogs, that is about 9.5 years for small dogs, 9.4 for medium, 8.9 for large and 7.8 for giant breeds. Breed matters: a French Bulldog is a senior from about 7, a Toy Poodle from about 10.5.

Do small dogs live longer than big dogs?

Usually, yes. In the same UK study, small breeds lived a median of 12.7 years, medium 12.5 and large 11.9; giant breeds such as Saint Bernards and Great Danes lived 9 to 11 years. Flat-faced breeds live shorter lives than their size suggests.

How can I tell how old my rescue dog is?

A vet estimates it from the teeth, the eyes, the coat and the body. Use their estimate as the date of birth in the calculator; the life stage will be close even if the exact birthday is not known.

How accurate is a dog age calculator?

It is a guide, not a diagnosis. Charts show the average dog of a size; your dog’s genes, weight and health move its real biological age up or down. Your vet is the best judge of your dog’s health.

Sources

• American Kennel Club, “How to Calculate Dog Years to Human Years” (chart based on AVMA guidance).
• Wang T. et al., “Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome,” Cell Systems 11 (2020): 176–185.
• McMillan K. M. et al., “Longevity of companion dog breeds: those at risk from early death,” Scientific Reports 14 (2024): 531.
• Creevy K. E. et al., “2019 AAHA Canine Life Stage Guidelines,” Journal of the American Animal Hospital Association 55 (2019): 267–290.

This calculator is for information only and is not veterinary advice.