Dog Age in Human Years: Chart by Size and How to Calculate It

The chart below gives the human-age equivalent for every year from 1 to 15, by size class. After it, you’ll find how the numbers are worked out, what veterinarians mean by “senior,” what the newer DNA research says, and how to use your dog’s age to plan care.

Dog age in human years chart

These figures use the same formulas as our free Pet Age Pro app, rounded down to whole years. Flat-faced (brachycephalic) breeds such as Pugs and French Bulldogs get their own column because their health profile differs from other dogs of the same weight.

Figures above 100 simply mean the dog has outlived the typical lifespan for its size. Few giant-breed dogs reach their teens.

Which column is my dog?

Pet Age Pro assigns each breed to a class. A few common examples from the app’s breed list:

• Small: Chihuahua, Yorkshire Terrier, Pomeranian, Shih Tzu, Dachshund
• Medium: Beagle, Cocker Spaniel, Border Collie, Australian Shepherd
• Large: Labrador Retriever, Golden Retriever, German Shepherd, Boxer, Rottweiler, Siberian Husky, Bernese Mountain Dog
• Giant: Great Dane, Mastiff, Saint Bernard, Newfoundland
• Flat-faced: Pug, French Bulldog, Bulldog, Boston Terrier

If your dog is a mix and you’re not sure, pick the column that matches their adult size. A dog of unknown mix that is neither tiny nor very big fits the medium column.

Have a cat as well? Cats use a single formula regardless of breed. See our cat age in human years chart.

How to calculate your dog’s age in human years

The calculation has three parts:

1. Year one counts for 15 human years in small and medium dogs, 12 in large and flat-faced dogs, and 10 in giant breeds.
2. Year two adds 9 (small and medium), 7 (large), 8 (flat-faced) or 6 (giant).
3. Every year after that adds 5 (small), 6 (medium or flat-faced), 7 (large) or 8 (giant).

Example: a Beagle (medium) who is 6½ years old. Year one gives 15, year two adds 9 (total 24), and the remaining 4½ years add 4.5 × 6 = 27. That makes 51 in human terms.

Notice that big dogs start “younger” and finish “older.” Large and giant breeds take longer to reach physical maturity, so their first two years count for less. Later on they age faster, which is why their columns overtake the small-dog column by about age five.

This shape lines up with the guideline the American Veterinary Medical Association (AVMA) popularized and the American Kennel Club still cites: about 15 human years for a medium dog’s first year, about 9 for the second, and roughly 5 per year after that, with larger dogs ageing faster in later life.

Why the “multiply by 7” rule doesn’t work

Multiplying by seven makes a 1-year-old dog a 7-year-old child. In reality most 1-year-old dogs are close to adult size and many are sexually mature, which is far closer to a human teenager. At the other end, the rule makes every 10-year-old dog 70, whether it is a Chihuahua that may live several more years or a Great Dane that is already well past the typical lifespan for its size.

Size is the main reason. Across breeds, bigger dogs tend to have shorter lives. The AKC summarizes research that linked roughly every 4.4 pounds (2 kg) of body mass to about a month less life expectancy. Our chart’s different columns are an attempt to capture that pattern.

What the DNA research says

In 2020, a team led by researchers at the University of California San Diego published a study in Cell Systems that compared age-related chemical changes in DNA (methylation) in 104 dogs, mostly Labrador Retrievers, with the same changes in people. They proposed a formula: human age = 16 × ln(dog age) + 31, where “ln” is the natural logarithm.

That formula ages young dogs very quickly. It puts a 1-year-old Labrador at about 31 human years, a 2-year-old at about 42, and a 12-year-old at about 71. Two points to keep in mind:

• It was built mainly from one breed, so it doesn’t try to account for size differences.
• It describes molecular ageing, not behaviour or care needs. A 1-year-old dog doesn’t act like a 31-year-old.

For everyday decisions, the size-based chart above is easier to use and reflects the fact that small and large dogs age differently. Both approaches agree on the big picture: dogs age fast early on, and the seven-year rule underestimates how quickly they mature.

Life stages: when is a dog a puppy, adult or senior?

Human-year equivalents are a helpful picture, but veterinarians plan care around life stages. The American Animal Hospital Association (AAHA) 2019 Canine Life Stage Guidelines describe five:

• Puppy: birth until rapid growth stops, around 6–9 months depending on breed and size. (Bringing home a young puppy? Our puppy potty schedule by age covers how often they need to go out.)
• Young adult: from the end of rapid growth until physical and social maturity, which most dogs reach by 3 to 4 years.
• Mature adult: from maturity until the last 25% of the dog’s estimated lifespan.
• Senior: the last 25% of estimated lifespan.
• End of life: the final stage, which depends on the dog’s specific health problems.

Because “senior” is tied to lifespan, a giant breed reaches it years earlier than a toy breed. As a simple rule of thumb, AAHA’s pet-owner guidance treats dogs over 7 as seniors, and Pet Age Pro uses the same cut-off: under 1 is a puppy, 1 to 7 is an adult, and 7 and up is a senior. The AKC notes that large dogs are often considered senior at 5 to 6 years, so if you have a big dog, start thinking about senior care sooner.

Using your dog’s age to plan care

Knowing your dog’s rough human-age equivalent is most useful when it changes what you do. A few practical points:

• Check-up frequency. AAHA recommends that senior dogs (over 7) see their veterinarian every six months, even if they seem healthy. Younger adults usually need a yearly wellness visit.
• Weight. Extra weight is easier to prevent than to lose, and it puts strain on joints as dogs age. Weigh your dog regularly and ask your vet what a healthy body condition looks like for your breed.
• Diet and exercise. Energy needs change from puppyhood to adulthood to the senior years. Talk to your vet before switching to a “senior” food, since there is no single standard for what that label means.
• Breed risks. Many breeds have known health issues, such as hip dysplasia in several large breeds or breathing problems in flat-faced dogs. Your vet can tell you which screening tests make sense and when.

When to call your vet

Age alone isn’t an illness, but some changes in older dogs need a prompt check rather than waiting for the next routine visit:

• Drinking or urinating much more than usual (see how much water a dog should drink a day)
• Weight loss or gain you can’t explain
• Stiffness, limping or reluctance to climb stairs or jump
• Coughing, faster breathing at rest, or tiring quickly on walks
• Confusion, getting stuck in corners, or changes in sleep patterns
• New lumps, bad breath, or trouble eating

If something seems off, call your veterinarian. This guide is general information and isn’t a substitute for professional advice about your own dog.

FAQ

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

About 15 human years for small and medium dogs, 12 for large and flat-faced breeds, and 10 for giant breeds. Most 1-year-old dogs are physically close to adult size, a bit like a human teenager.

Is one dog year really seven human years?

No. Dogs age much faster than that in their first two years and then slow down. How fast they age after that depends mostly on size, with large and giant breeds ageing faster.

At what age is a dog considered a senior?

Veterinary guidelines define senior as the last 25% of a dog’s expected lifespan. In practice, many vets treat dogs over 7 as seniors, and large or giant breeds often reach that stage around 5 to 6.

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

Using the chart above: about 64 for a small dog, 72 for a medium dog, 75 for a large dog, 80 for a giant breed, and 68 for a flat-faced breed.

Are human-year equivalents exact?

No. They are estimates that help you picture your dog’s life stage. Genetics, size, weight, diet and medical care all affect how an individual dog ages.

Sources

• American Animal Hospital Association. 2019 AAHA Canine Life Stage Guidelines: canine life stage definitions.
• American Animal Hospital Association. Supporting your senior pet: veterinary care recommendations.
• American Kennel Club. How to calculate dog years to human years (cites the AVMA guideline).
• Wang T, et al. Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome. Cell Systems, 2020. Preprint on bioRxiv.

Written by Jordan Ellis for AppSphere Solutions. Researched against the veterinary and scientific sources listed above. See how we research our guides, or browse more pet care guides.