How old is my dog in human years? Dog age calculator by size
Work out your dog's age in human years based on size. Why the "multiply by 7" rule doesn't work, and when a dog becomes a senior.
Enter your dog's age and adult size. The calculator uses the American Veterinary Medical Association (AVMA) guideline: a dog's first year equals about 15 human years, the second adds about 9 more, and after that each year adds 4 to 7 human years depending on size.
Why "multiply by 7" doesn't work
The famous "one dog year equals seven human years" rule is a myth. Dogs mature very quickly at first: by one year old they're young adults able to reproduce, which in a person corresponds to the teenage years. After that they age more slowly, but not all at the same pace.
Why size matters
Large dogs live fewer years on average than small ones and age sooner. So from age two, the calculator adds:
| Adult size | Human years per year after the second |
|---|---|
| Small (up to 20 lb) | About 4 |
| Medium (21-50 lb) | About 5 |
| Large (51-90 lb) | About 6 |
| Giant (over 90 lb) | About 7 |
A common approximation based on the AVMA guideline for a medium dog (15 human years in the first year, 24 at two, and about 5 more each year). For other sizes we adjusted that figure up or down. Every dog is different: genetics, weight and care matter too.
The newest scientific formula
In 2020, researchers at the University of California San Diego compared how DNA changes with age in dogs and people, and proposed this formula: human age = 16 × ln(dog's age) + 31. By that measure, a 1-year-old dog compares to a person of about 31, and a 10-year-old dog to about 68. The study only included Labrador retrievers, so we show it as a bonus next to the main result.
When is a dog a senior?
As a rule of thumb, small and medium dogs are considered seniors around age 7, and large and giant dogs around 5 to 6. From then on, it's a good idea to:
- Schedule more frequent checkups, with blood and urine tests, to catch kidney, liver or heart problems early.
- Adjust portions: many older dogs burn fewer calories. Work it out with our pet food calculator.
- Keep an eye on their teeth, joints and weight.
Vet costs tend to rise for older dogs: see the annual cost of owning a dog.
Frequently asked questions
How old is a 1-year-old dog in human years?
About 15 human years, whatever their size. At 2, about 24.
How old is a 10-year-old dog in human years?
It depends on size: about 56 for a small dog, 64 for a medium dog, 72 for a large dog and 80 for a giant breed.
How long do dogs live?
It depends mostly on size and breed: small dogs generally live longer than large ones. Good care (healthy weight, vaccines, parasite prevention and checkups) helps them live longer and better.
Sources
This calculator gives a rough estimate based on the sources cited. It doesn't replace the judgment of a veterinarian who knows your pet.
