Dog Age Calculator

This calculator converts your dog's age into an approximate human-equivalent age, adjusted for adult size. It also shows the life stage, a rough life expectancy for that size of dog, the years that leaves, and how many human years each dog year currently represents.

Size matters because large dogs age faster. Small breeds often live into their mid-teens, while giant breeds such as Great Danes and Irish Wolfhounds are often considered old by 7 or 8. All dogs, though, grow up very quickly: by their second birthday most are physically and sexually mature, which is why the old "one dog year equals seven human years" rule badly underestimates young dogs and overestimates small older ones.

Choose the size band by your dog's expected adult weight, not its current weight. For mixed breeds, go by weight rather than appearance. Figures are averages; genetics, weight and care can add or take away years. To estimate how big a puppy will get, use the puppy weight calculator; for cats, the cat age calculator uses feline ageing rates.

The 15-then-9 pattern for the first two years is the guideline used by the American Veterinary Medical Association; later rates by size are simplified from size-based veterinary ageing charts. A 2020 study of DNA methylation in Labrador retrievers (Wang et al., Cell Systems) proposed a different curve, human age ≈ 16 × ln(dog age) + 31, which ages young dogs even faster and is so far validated for one breed only. Life stages follow the idea in the AAHA Canine Life Stage Guidelines that the senior stage is the last part of a dog's expected lifespan, so it starts earlier for big breeds.

Calculated with the formula above. Read across from your dog's age to the column for its adult size.

Across most mammal species, bigger animals live longer, but within dogs the reverse holds: large and giant breeds have shorter lives. Researchers link this to their very fast growth as puppies and higher rates of age-related disease such as cancer, heart disease and joint problems. The calculator uses rough average life expectancies of 15 years for small dogs, 13 for medium, 11 for large and 9 for giant breeds. Individual breeds vary widely within each band; flat-faced breeds, for example, tend to have shorter lives than their size would suggest.

• Puppy and adolescent (under 2): vaccinations, socialization, training and growth-appropriate food; large breeds need controlled growth to protect their joints.
• Adult: keep a lean body shape. Lean dogs live longer on average, and the dog food calculator helps set daily portions.
• Mature: annual or twice-yearly check-ups, dental care and watching for stiffness or weight change.
• Senior: twice-yearly vet visits, blood and urine tests, softer bedding, ramps or steps, and shorter, more frequent walks. Changes in thirst, appetite, breathing or behavior are worth reporting early.