Dog Age Calculator: Dog Years to Human Years
How old is your dog in human years? Choose their size, then enter their age or birthday. You'll get their age in human years from the chart vets use, plus their life stage and care tips. Or switch it round to find your own age in dog years.
Dog's size (adult weight)
Your dog
Coat colour (just for fun)
Your age
Find out how old you'd be as a dog of the size you picked.🔒 Everything is worked out in your browser. Nothing is saved or sent anywhere.
To save a PDF, choose "Save as PDF" as the printer. It includes the details you entered and the result.
How to convert dog years to human years
Dogs grow up very quickly, then age at different speeds depending on their size. Bigger dogs age faster than small ones. Vets use this rule:
- First year: about 15 human years (about 12 for giant breeds).
- Second year: add about 9 human years, so most 2-year-old dogs are about 24.
- Every year after that: add about 4 years for small dogs, 4–5 for medium, 5–6 for large and about 7 for giant dogs.
So a 10-year-old Chihuahua is about 56 in human years, a 10-year-old Beagle about 60, a 10-year-old Labrador about 66 and a 10-year-old Great Dane about 79. The calculator above uses the full size-by-size chart below.
How to convert human years to dog years
Choose Human to dog above. The calculator reads the same chart backwards for the size you pick. As a quick guide, a 40-year-old person would be about 6 years old as a medium-sized dog, or about 4 as a giant dog.
Dog age chart: dog years to human years by size
Based on the widely used size chart from American veterinary guidance. Figures are approximate, and every dog is an individual.
The new DNA formula for dog years
In 2019, scientists at the University of California, San Diego compared chemical changes in the DNA of Labrador retrievers and people as they age. They suggested: human age = 16 × ln(dog age) + 31, where ln is the natural logarithm. By this formula, a 1-year-old dog is already about 31, because dogs mature so fast. After that, ageing slows down a lot. The study looked at only one breed, so most vets still use the size chart. The calculator shows both for comparison.
Dog life stages
These stages follow the life-stage guidelines vets use. Large and giant dogs move through them sooner than small dogs.
Frequently asked questions
Is one dog year equal to seven human years?
No, that's a myth. A 1-year-old dog is more like a 15-year-old person, because puppies mature very fast. After that, the speed depends on size. A small dog adds about 4 human years each year, while a giant dog adds about 7.
Why do big dogs age faster than small dogs?
Scientists aren't completely sure. One idea is that large breeds grow so quickly that their bodies age sooner. Whatever the reason, small dogs usually live longer. Many small breeds reach 12–16 years, while giant breeds more often live 8–10 years.
How accurate is this dog age calculator?
It uses the standard size chart vets use, so it's a good guide. Genes, breed, diet, weight and exercise all affect how an individual dog ages, and your vet can tell you most about your own dog.
My dog is a mixed breed. Which size should I choose?
Choose the size based on your dog's adult weight. If they're still a puppy, use the weight your vet expects them to reach, or the size of their parents if you know it.
How can I tell how old a rescue dog is?
A vet can estimate age from the teeth, eyes, coat and joints. Puppies can be aged quite precisely by their teeth. For adult dogs it's a best guess, so choose a birthday that matches and celebrate it.
How do I keep my dog healthy as they get older?
Regular vet check-ups, a healthy weight, dental care, daily walks and games to keep the mind busy make the biggest difference. Older dogs also love soft, supportive beds, non-slip floors and shorter, more frequent walks.
This calculator is for fun and general guidance only. It isn't veterinary advice. For questions about your dog's health, please talk to your vet.