Pet Age Calculator
A dog's or cat's age in human years from the AAHA physiological age chart, by dog size, with its life stage.
Result…
How it's calculated
Human years = chart value at the age, read in a straight line between the chart's rows Chart (AAHA poster): cats 6 months = 10, 1 year = 15, 2 = 24, then + 4 a year; dogs 1 = 15, 2 = 24, then by size Dog senior ≈ the last 25% of expected lifespan (AAHA)
Converts a dog's or cat's age into human years with the physiological age chart published by AAHA (the American Animal Hospital Association), which adapts the AAFP–AAHA feline life stage guidelines for cats and the Dog Owner's Home Veterinary Handbook for dogs. Both species age fast early on: 15 human years in the first year and 24 by the second. After that a cat adds about 4 a year, while a dog adds 4 to 8 a year depending on its adult size, because big dogs age faster. Ages between the chart's yearly rows are read in a straight line; under the first row and past the last, the result is a labelled estimate. The life stage follows AAHA's canine and feline life stage guidelines, and for dogs the AVMA's average senior ages by size. The old rule of seven human years per dog year is shown only for comparison.
Your numbers, step by step
About the Pet Age calculator
This pet age calculator converts a dog's or cat's age into human years using the physiological age chart published by AAHA, the American Animal Hospital Association. Dogs are read by adult size, because large and giant breeds age faster than small ones; cats have one scale. Ages between the chart's yearly rows are read in a straight line, and ages below its first row or past its last are clearly marked as estimates. It also names the life stage, from puppy or kitten to senior, following AAHA's canine and feline life stage guidelines, and for dogs either 75% of an expected lifespan you enter or the AVMA's average senior ages for the size. Pet owners use it to make sense of a birthday, to think about senior check-ups, or just out of curiosity. The working shows the chart rows used. For feeding, the pet calorie calculator estimates daily needs.
How to use it
- Choose “Dog” or “Cat” under “Pet”.
- For a dog, pick the “Adult size” by the weight it is or will be as an adult, in kg or lb.
- Enter “Age: years” and “Age: months”.
- Optionally, enter the “Expected lifespan for the breed” so the senior stage is set at the last 25% of it.
- Read the age in human years, the life stage and how many human years each year adds at this age.
Worked example
A large dog of 23 to 40.8 kg (51 to 90 lb) aged 6 years 6 months sits halfway between the chart's 45 at 6 years and 50 at 7 years, so it is about 47.5 in human years, a mature adult. A cat aged 14 reads straight off the chart as 72, which is the senior stage (over 10 years). The old rule of 7 would have said 98 for that cat.
Updated
Questions people ask
How do I convert dog years to human years?
Use a size-based chart rather than multiplying by 7. On the AAHA chart a dog's first year is 15 human years and its second brings it to 24, after which small dogs add about 4 a year and giant dogs up to 8.
How old is a cat in human years?
On the AAHA chart a cat is 15 at 1 year and 24 at 2, then adds 4 human years a year: 10 years is 56 and 15 years is 76.
Is one dog year really seven human years?
No. Dogs mature much faster in their first two years and then age at a pace that depends on size, so the 7 × rule overstates young dogs' ages and misses the difference between breeds.
When is a dog or cat a senior?
AAHA treats cats as senior after 10 years. For dogs it is the last 25% of the expected lifespan; the AVMA's averages are 8 to 11 years for small breeds and 6 to 7 for giant breeds.
How accurate is a pet's age in human years?
It is a rough comparison, not a health measure: breed, genetics, weight and care all change how a pet ages. Your veterinarian can tell you how your pet is doing and when to start senior check-ups.