How to use the dog age calculator
- Enter your dog’s age in years, and any extra months.
- Choose its adult size. For a puppy, choose the size it will be as an adult.
- Read the age in human years from the AAHA chart. Below it you will see the DNA-clock result, the old “× 7” result for comparison, and your dog’s life stage.
The formula
The AAHA chart. The American Animal Hospital Association’s age chart (published with its 2019 Canine Life Stage Guidelines) gives a human-equivalent age for each year, in four weight groups: up to 20 lb (9 kg), 21–50 lb, 51–90 lb and over 90 lb. Every dog is 15 at one year and 24 at two. After that the groups split, because larger dogs age faster. Between whole years the calculator moves in a straight line, so 7½ years is halfway between the 7 and 8 year values.
| Dog’s age | Up to 20 lb | 21–50 lb | 51–90 lb | Over 90 lb |
|---|---|---|---|---|
| 3 years | 28 | 28 | 30 | 32 |
| 5 years | 36 | 37 | 40 | 42 |
| 7 years | 44 | 47 | 50 | 56 |
| 10 years | 56 | 60 | 66 | 78 |
| 13 years | 68 | 74 | 82 | 101 |
| 16 years | 80 | 87 | 99 | 123 |
The DNA-clock formula. Wang and colleagues (Cell Systems, 2020) compared the chemical changes on DNA as dogs and people age and fitted: human age = 16 × ln(dog age) + 31. It was built from Labrador Retrievers, so treat it as an interesting second opinion rather than a rule for every breed. It only works from age 1.
Life stage follows the AAHA guidelines: puppy, young adult (to about 3–4 years), mature adult, and senior for the last 25% of the expected lifespan for the dog’s size.
Tips
- Size matters more than breed here. The chart is by weight, so a mixed breed works just as well as a purebred.
- Senior check-ups. Vets usually suggest more frequent check-ups and blood tests once a dog is a senior.
- Compare with cats. Cats age on a different curve; see the cat age calculator.
- Lifespan by breed. The dog life expectancy calculator shows the typical lifespan for 49 breeds.
Sources
- American Animal Hospital Association (AAHA): canine and feline age chart, 2019 Canine Life Stage Guidelines.
- Wang T. et al. (2020). Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome. Cell Systems 11: 176–185.
- McMillan K.M. et al. (2024). Longevity of companion dog breeds: those at risk from early death. Scientific Reports 14: 531.
Frequently asked questions
How old is my dog in human years if he is 7?
It depends on size. On the AAHA chart a 7-year-old dog is 44 in human years if it weighs 20 lb (9 kg) or less, 47 if it weighs 21–50 lb, 50 if it weighs 51–90 lb and 56 if it is over 90 lb. The 2020 DNA-clock formula gives about 62.
How are dog years calculated?
Vets use charts that count the first year as about 15 human years and the second as about 9 more (24 in total). After that each year adds roughly 4 to 5 human years for small and medium dogs and up to 7 or 8 for giant breeds, because big dogs age faster. A 2020 study also proposed a DNA-based formula: 16 × ln(dog age) + 31.
How much is 1 dog year in human years?
The first year of a dog’s life is about 15 human years on the AAHA chart, for every size. A one-year-old dog is roughly like a mid-teenager: physically grown or nearly grown, but not fully mature.
Is the "multiply by 7" rule accurate?
No. It makes young dogs too young and old small dogs too old. A 2-year-old dog is about 24 in human years, not 14, while a 10-year-old small dog is about 56, not 70. Charts by size are much closer.
How long do dogs live on average?
A 2024 study of 584,734 dogs in the UK (McMillan et al., Scientific Reports) found a median lifespan of 12.5 years. Small breeds tended to live longer than large ones, and the median ranged from 5.4 years in the Caucasian Shepherd Dog to 15.4 years in the Lancashire Heeler.