How to use the dog age calculator
- Enter your dog's age in years and months.
- Choose your dog's size as an adult. For mixed breeds, use their current (or expected) adult weight.
- See your dog's age in human years, its life stage and the full chart for its size.
How dog years are calculated
Dogs mature very quickly: a one-year-old dog is roughly as developed as a 15-year-old human, and a two-year-old as a 24-year-old. After that, each dog year counts for about 4 to 7 human years depending on size — larger breeds age faster and have shorter life spans than small breeds.
Example: a 5-year-old medium dog is about 36 in human years. At 10, a small dog is about 56, while a large dog is about 66.
Dog years to human years chart
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 |
| 2 | 24 | 24 | 24 | 22 |
| 3 | 28 | 28 | 28 | 31 |
| 4 | 32 | 32 | 32 | 38 |
| 5 | 36 | 36 | 36 | 45 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 79 |
| 12 | 64 | 69 | 77 | 93 |
| 14 | 72 | 78 | 88 | 107 |
| 16 | 80 | 87 | 99 | 121 |
The DNA-based formula
A 2020 study from the University of California San Diego compared changes in DNA (epigenetic aging) in Labrador retrievers and humans and proposed human age = 16 × ln(dog age) + 31. It suggests dogs age especially fast early on: a 1-year-old dog is like a 31-year-old human. Because it was based on a single breed, the size-based chart above is still the more common reference.
Is "one dog year = seven human years" true?
No. The 7:1 rule probably came from comparing average life spans (about 10–13 years for dogs versus 70–80 for people). It overestimates the age of older small dogs and underestimates young dogs of every size.
When is a dog a senior?
Many veterinarians consider small dogs seniors from about 10 years, medium dogs from about 8, large dogs from about 7 and giant breeds from about 6. Senior dogs benefit from twice-yearly checkups, joint-friendly exercise and a diet suited to their age.
Frequently asked questions
How old is my dog in human years?
It depends on size. Most dogs reach about 15 human years at age 1 and 24 at age 2. After that, small dogs add about 4 years per year and large dogs 5 to 6.
Is one dog year equal to seven human years?
No. That old rule of thumb is too simple. Dogs age fastest in their first two years and larger breeds age faster than small ones.
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.
Why do large dogs age faster?
Researchers are still studying it, but large breeds grow very fast and appear to develop age-related diseases earlier, which shortens their average life span.
How long do dogs live?
Small breeds often live 12 to 16 years, medium breeds 10 to 14, large breeds 9 to 12 and giant breeds 7 to 10, with wide variation between individual dogs and breeds.
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