Dog Age Calculator
The old "multiply by 7" rule is wrong. Dogs grow up very fast in their first two years, and big dogs age faster than small dogs. Enter your dog's age and size to get a realistic human-age equivalent.
How the dog age calculator works
The American Veterinary Medical Association guideline (as summarized by the American Kennel Club) counts a dog's first year as about 15 human years and the second year as about 9 more, so a 2-year-old dog is roughly 24 in human terms. After that, a medium-size dog adds about 5 human years per year. Because large dogs age faster, this calculator adds 4 years per year for small dogs, 5 for medium, 6 for large and 7 for giant breeds.
Year 1: 15 human years
Year 2: +9 (total 24)
Each year after: +4 small · +5 medium · +6 large · +7 giant
We also show the DNA-clock formula from a 2020 University of California San Diego study of Labrador retrievers, which compared chemical changes on dog and human DNA: human age = 16 × ln(dog age) + 31. It makes young dogs look "older" than the classic chart does.
Dog years to human years chart
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 4 | 32 | 34 | 36 | 38 |
| 6 | 40 | 44 | 48 | 52 |
| 8 | 48 | 54 | 60 | 66 |
| 10 | 56 | 64 | 72 | 80 |
| 12 | 64 | 74 | 84 | 94 |
| 14 | 72 | 84 | 96 | 108 |
When is a dog a senior?
Size is the biggest factor. Giant breeds can be considered senior at about 5–6 years, large breeds around 7, medium dogs around 8 and small dogs around 10. Senior dogs benefit from vet checkups at least twice a year, because problems such as arthritis, kidney disease and dental disease are easier to manage when found early.
Frequently asked questions
Is one dog year really seven human years?
No. The "7 years" rule is a myth. Dogs reach adulthood within their first year or two, so a 1-year-old dog is closer to a 15-year-old human. After that, aging slows and depends on size.
How old is a 10-year-old dog in human years?
With the size-adjusted method, about 56 for a small dog, 64 for a medium dog, 72 for a large dog and 80 for a giant breed.
Why do big dogs age faster?
Large and giant breeds grow very quickly and tend to have shorter lifespans. Researchers are still studying why, but the pattern is clear across breeds, which is why size changes the conversion.
Which formula is more accurate?
Neither is exact. The classic size chart is easy to use and accounts for size. The DNA-clock formula is based on molecular research but was developed in one breed (Labradors). Use them as a rough guide.
Sources
- American Kennel Club — How to calculate dog years to human years (AVMA guideline)
- AVMA — Senior pets
- Wang T. et al. (2020), Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome, Cell Systems