Dog Years Calculator
Convert your dog’s age to human years using the size-based vet chart (small to giant) and the UC San Diego DNA-methylation formula.
The old rule that one dog year equals seven human years is wrong in both directions: dogs grow up far faster than that in their first two years, then age more slowly, and big dogs age faster than small ones. This calculator converts your dog’s age into human years with the size-based chart used by vets and the AKC, and shows the newer DNA-methylation formula from UC San Diego alongside it.
How to use this tool
- Enter your dog’s age in years and months.
- Choose the size group that matches its adult weight.
- Read the human-equivalent age; the table lists every year from 1 to 16 for all four sizes.
Formula
Size chart: about 15 human years at age 1 (12 for giant dogs) and 24 at age 2 (22 for giant dogs), then roughly 4–7 human years per dog year depending on size. Epigenetic clock: human age = 16 × ln(dog age) + 31
Between whole years the chart value is interpolated in a straight line. The epigenetic formula comes from Wang et al. (2020), who compared age-related DNA methylation in 104 Labrador Retrievers with people; ln is the natural logarithm. This calculator shows that comparison only from age 1, rather than using it to assign a numerical age to a rapidly developing puppy.
Example
A 7-year-old medium dog (21–50 lb) is about 47 in human years on the size chart. A large dog of the same age is about 50 and a giant dog about 56. The epigenetic formula gives 16 × ln 7 + 31 ≈ 62, and the old seven-times rule would say 49.
Frequently asked questions
Is one dog year really seven human years?
No. A one-year-old dog is already close to physically mature, so the AKC’s guideline puts the first year at about 15 human years and the second at about 9 more. After that each year counts for roughly 4 to 7 human years, depending on size.
Why do large dogs age faster?
Large and giant breeds have shorter average lifespans, so from middle age on each calendar year covers more of their life. On the chart a 10-year-old giant dog is about 79, while a small dog of the same age is about 56.
Which result should I trust?
Both are estimates. The size chart reflects lifespan differences between sizes; the epigenetic clock matches DNA-methylation changes and was built from a single breed. Neither replaces your vet’s view of how your dog is actually ageing.
What size is my dog?
Use its healthy adult weight: small is 20 lb (about 9 kg) or less, medium 21–50 lb, large 51–100 lb and giant over 100 lb (about 45 kg).
Sources
This tool gives an estimate for general information only. It is not financial, tax, legal or medical advice — check with a qualified professional before you rely on the result.
Last updated: 2026-10-30