Dog Age Calculator
Convert your dog's age into human years. Enter your dog's age and breed size to see its human-year equivalent, life stage, and how that compares to the old 'multiply by 7' rule and the 2020 epigenetic-clock formula.
Age in human years
≈ 39 human years
- Life stage
- Adult
- Ageing rate after age 2
- 5 human years per dog year
- Old “multiply by 7” estimate
- ≈ 35 human years
- Epigenetic-clock estimate (2020 study)
- ≈ 57 human years
Based on the AVMA guideline: the first dog year counts as about 15 human years, the second adds about 9 (24 total), then each later year adds 4–7 human years depending on breed size, with larger dogs ageing faster. All figures are rough estimates.
How to use this calculator
Enter your dog's age in years (and optionally the extra months), then pick the breed size that best fits its adult weight: small (up to 20 lb / 9 kg), medium (21–50 lb), large (51–100 lb), or giant (over 100 lb / 45 kg). The calculator returns the human-year equivalent using the American Veterinary Medical Association guideline, the life stage (puppy, adult, or senior), and two comparison figures — the naive 'multiply by 7' folk rule and the 2020 epigenetic-clock formula — so you can see how the estimates differ. If you are unsure of the size, medium is a reasonable default.
How the calculation works
The calculator uses the AVMA rule popularised by the American Kennel Club: a dog's first year counts as roughly 15 human years, the second year adds about 9 more (24 in total), and every year after that adds a further 4 to 7 human years depending on breed size. Small dogs age most slowly, giant breeds fastest, which is why a small and a giant dog of the same age can be a decade apart in human terms. Two alternatives are shown for context: the old ×7 rule (age × 7), which badly overstates the early years, and the epigenetic clock from a 2020 Cell Systems study, human age = 16 × ln(dog age) + 31, based on DNA methylation in Labrador retrievers. Every figure is a rough estimate — individual health, breed, and lifestyle all shift the real number.
Worked example
Take a 5-year-old medium-sized dog. Year one is 15 human years and year two brings the total to 24. The three years after that each add 5 human years for a medium breed, so 24 + 3 × 5 = 39 human years. A giant breed of the same age would be 24 + 3 × 7 = 45, while a small breed would be 24 + 3 × 4 = 36 — the same birthday, but a 9-year human gap. For comparison, the ×7 rule gives just 35, and the epigenetic formula gives 16 × ln(5) + 31 ≈ 57.
Frequently asked questions
Is one dog year really equal to seven human years?
No — the '1 dog year = 7 human years' rule is a myth that has stuck around for decades. Dogs mature far faster in their first two years and then age more gradually, so the relationship is not a straight multiplication. A one-year-old dog is closer to a 15-year-old human than a 7-year-old, and by old age the ×7 rule undercounts. Vets now use the AVMA curve this calculator is built on, which treats the first two years specially and then adds 4–7 human years per dog year by size.
Why does breed size change the result?
Larger dogs have shorter lifespans and reach old age sooner, so each of their later years is worth more human years. A small dog is generally considered senior around age 10, a large dog around 7, and a giant breed as early as 6. This calculator reflects that by adding 4 human years per dog year for small breeds, 5 for medium, 6 for large, and 7 for giant breeds once the dog is past its second birthday. If you do not know the size, medium is a safe middle estimate.
How old is a 1-year-old or 2-year-old dog in human years?
A one-year-old dog is roughly 15 in human years, regardless of size — the first year covers puppyhood through to the equivalent of a mid-teenager. By two years old a dog is about 24 in human terms. After that the paths diverge by size, but those first two milestones are broadly the same for all breeds. This is why puppies seem to grow up so quickly: most of their fast ageing happens before their second birthday.
What is the epigenetic-clock formula the calculator shows?
In 2020, researchers at the University of California San Diego published a formula in Cell Systems based on DNA methylation — chemical marks on DNA that change predictably with age. Their equation is human age = 16 × ln(dog age) + 31. It maps a 1-year-old dog to about a 31-year-old human and a 7-year-old dog to roughly 62. It was derived from Labrador retrievers, so it is a single-breed model, but it is the most biologically grounded estimate available and is shown here for comparison alongside the AVMA guideline.
When is my dog considered a senior?
It depends on size. Small breeds are usually classed as senior from about 10 years, medium breeds from 8, large breeds from 7, and giant breeds from 6. The calculator labels your dog puppy, adult, or senior based on its age and the size you select. Senior status is a cue to talk to your vet about more frequent check-ups, joint support, and diet — not a sign anything is wrong. Many dogs live happy, active lives well into their senior years.
How accurate is a dog age calculator?
It is an estimate, not a diagnosis. Even veterinary charts describe these conversions as rough, because ageing varies with breed, genetics, weight, diet, dental health, and care. Two dogs the same age can differ by years biologically. Use the human-year figure as a guide to your dog's life stage and care needs rather than an exact age. Your vet can give a more tailored assessment based on a physical exam.