Dog Age Calculator

Turn your dog’s age into human years. The answer depends on size, because big dogs race through middle age while small dogs take their time.

Your dog

Size by
Size group

Medium: 21–50 lb (9.5–23 kg)

39human years

A 5-year-old medium dog is about as mature as a 39-year-old person.

Mature adultDNA formula: 57×7 myth: 35

Annual exams with dental checks; watch weight and joint stiffness.

How the calculation works

PawCalc uses the size-based approach many vets use with the AAHA Canine Life Stage Guidelines: the first year counts as about 15 human years, because a one-year-old dog is already physically mature. The second year adds about 9. After that, each dog year adds:

  • 4 years for small dogs (up to 20 lb)
  • 5 years for medium dogs (21–50 lb)
  • 6 years for large dogs (51–90 lb)
  • 7 years for giant dogs (over 90 lb)

The chip labelled “DNA formula” uses the epigenetic clock from Wang et al. (Cell Systems, 2020): 16 × ln(age) + 31. It was built from Labrador retrievers, so treat it as a second opinion, especially for toy and giant breeds.

Use the adult weight your dog is (or will be) at maturity, not a puppy’s current weight. Mixed breed? Pick the size group closest to their adult weight.

Why “multiply by seven” gets dogs wrong

Drag the age and change the size. The ×7 line is straight, but real dogs age in a curve: very fast at first, then steadily, and faster for big dogs.

Size
0204060801001200246810121416Dog age (years)
×7 mythSize rule (large)DNA clock (Labradors)
42×7 myth
48Size rule
60DNA clock

In the middle years the lines run close together, which is why ×7 feels roughly right for a large dog around age 6. It is the ends where it fails.

Dog age chart: dog years to human years

Human-year equivalents by size group, using the size-based method above.

Dog ageSmallMediumLargeGiant
115151515
224242424
328293031
432343638
536394245
640444852
744495459
848546066
952596673
1056647280
1160697887
1264748494
13687990101
14728496108
157689102115
168094108122

Ask a follow-up about your pet

Your question and the result above go to an AI model (via Vercel AI Gateway) to write a short, general answer. It is not a vet and can be wrong. Nothing is stored.

Questions owners ask

How old is my dog in human years?
Use the calculator above: enter your dog’s age and size. As a rule of thumb from the AAHA life-stage approach, a dog’s first year equals about 15 human years, the second adds about 9, and each year after adds 4 (small dogs) to 7 (giant dogs).
Is one dog year really seven human years?
No. The ×7 rule badly underestimates young dogs (a 1-year-old dog is sexually mature, like a teenager, not a 7-year-old child) and overestimates old small dogs. Size matters: big dogs age faster after their second year.
Why do large dogs age faster than small dogs?
Researchers still debate the mechanism, but the pattern is consistent: large and giant breeds grow fast, reach “senior” earlier and have shorter lifespans. A 2013 study in The American Naturalist (Kraus et al.) found large dogs appear to age at an accelerated pace.
What is the DNA (epigenetic) dog age formula?
A 2020 study in Cell Systems (Wang et al.) compared DNA methylation in Labrador retrievers and people and proposed human age = 16 × ln(dog age) + 31. It fits Labradors best and is less reliable for very young puppies or other body sizes, so PawCalc shows it as a second opinion.
When is a dog considered a senior?
AAHA’s 2019 Canine Life Stage Guidelines define senior as the last 25% of the expected lifespan. That is roughly 10–11 years for a small dog, 8–9 for a large dog, and as early as 6–7 for giant breeds.
What is the oldest a dog has lived?
Guinness World Records lists Bluey, an Australian cattle dog who died in 1939 at 29 years and 5 months, as the longest-lived dog with verified records.

Sources: AAHA 2019 Canine Life Stage Guidelines; Wang T. et al., “Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome”, Cell Systems 2020; Kraus C. et al., The American Naturalist 2013.

Keep going

Cat age calculatorCat years to human years, with the full age chart.Puppy weight calculatorHow big your puppy will get, from weight and age.Dog food calculatorDaily calories, cups and grams for your dog.