How to use it
- Enter your dog's age in years and months.
- Choose the adult size: small, medium, large or giant.
- Read the age in human years.
- Compare the methods and open the full chart.
Why size matters
The old rule of thumb says one dog year equals seven human years. It's simple, but it gets puppies and large breeds badly wrong. Dogs mature much faster than people at first: a one-year-old dog is roughly like a teenager, not a seven-year-old child. After that, small dogs age more slowly than big ones and usually live longer.
That's why the calculator asks for your dog's adult size:
| Size | Adult weight |
|---|---|
| Small | up to about 20 lb (9 kg) |
| Medium | about 21–50 lb (9.5–23 kg) |
| Large | about 51–100 lb (23–45 kg) |
| Giant | over 100 lb (45 kg) |
For a puppy, choose the size it will be as an adult. For a mixed breed, pick the size closest to its current adult weight.
The size-based chart
The main result uses the American Kennel Club's size-based chart, which builds on American Veterinary Medical Association guidance. A few values from it:
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 |
| 2 | 24 | 24 | 24 | 22 |
| 5 | 36 | 36 | 36 | 45 |
| 8 | 48 | 51 | 55 | 64 |
| 10 | 56 | 60 | 66 | 79 |
| 12 | 64 | 69 | 77 | 93 |
| 15 | 76 | 83 | 93 | 114 |
Between whole years the calculator interpolates, so 5 years and 6 months gives a value between the 5- and 6-year rows. Under one year it scales proportionally from zero, and beyond 16 years it extends the chart by the last yearly step. The full table from 1 to 16 years is available under the result, with your dog's row highlighted.
The epigenetic formula
In 2020, researchers led by Tina Wang published a study in Cell Systems that compared DNA methylation, a chemical marker that changes with age, in Labrador retrievers and humans. Their formula is:
human age = 16 × ln(dog age) + 31
where ln is the natural logarithm. It gives:
| Dog age | Human years |
|---|---|
| 1 | 31 |
| 2 | 42 |
| 4 | 53 |
| 7 | 62 |
| 10 | 68 |
| 14 | 73 |
The formula captures how fast young dogs age, but it was calibrated on a single breed and isn't defined for dogs under one year. The calculator shows it as a second opinion next to the chart, along with the old ×7 rule for comparison.
What the number is good for
A human-years figure is a friendly way to think about your dog's life stage: whether it's still a youngster, in its prime or a senior. It isn't a medical measurement. Breed, genetics, weight and health all affect how a dog ages, and individual dogs vary a lot.
Many vets consider dogs seniors from around 7 years, earlier for large and giant breeds. Senior dogs often benefit from more frequent checkups, joint care and diet changes, so if your dog is entering that stage, talk to your veterinarian.
The calculation runs in your browser. For cats, use the cat age calculator.
Frequently asked questions
How do I convert dog years to human years?
Enter your dog's age and choose its adult size. The calculator uses the AKC size-based chart; a 5-year-old medium dog is about 36 in human years.
Is one dog year really seven human years?
No. Dogs age much faster in their first two years and more slowly later, and big dogs age faster than small ones. The ×7 rule is only a rough average.
How old is a 10-year-old dog in human years?
About 56 for a small dog, 60 for a medium dog, 66 for a large dog and 79 for a giant breed, according to the AKC chart.
What is the epigenetic dog age formula?
Human age = 16 × ln(dog age) + 31, from a 2020 study of Labrador retrievers. It applies to dogs one year and older.
When is a dog considered a senior?
Often from around 7 years, and earlier for large and giant breeds. Your vet can advise based on your dog's breed and health.
Last updated: November 12, 2026