Dog and cat age calculator: how old is my pet in human years?
Ask your vet about your own pet. This page is general information from the sources below.
"One dog year equals seven people years" is wrong. A 2020 University of California San Diego study of 104 Labrador retrievers found dogs age fastest when young, with the formula 16 × ln(age) + 31 (Cell Systems). For cats, International Cat Care gives 15 at one year and 24 at two, then 4 per year.
Checked October 29, 2026.
Your dog is 4 years old: adult
A grown-up dog. A yearly vet visit is the usual minimum; ask your vet what yours needs.
About 53 in people years
Working: 16 × ln(4.00) + 31 = 53.2. This formula came from 104 Labrador retrievers, so it's best for Labs and is only a guide for other dogs. It starts at one year old.
Kid line: Your dog is about 53 in people years!
Happy birthday,
Your dog!
Your dog is 4 years old, about 53 in people years.
Why not multiply by 7?
The AAHA's dog guidelines say that, rather than work out human equivalents, vets use life stages: puppy, young adult, mature adult, senior and end of life, set by age and by the dog's size and breed (AAHA). A nine-month-old dog can already have puppies, which is not what a one-year-old person can do.
When is a dog a senior?
The AVMA says experts suggest a dog is senior in the last 25 percent of its expected life span, which averages out like this:
| Size | Weight | Senior from about |
|---|---|---|
| Small or toy | less than 20 pounds | 8 to 11 years |
| Medium | 20 to 50 pounds | 8 to 10 years |
| Large | 50 to 90 pounds | 8 to 9 years |
| Giant | more than 90 pounds | 6 to 7 years |
The AVMA also says cats are generally considered senior after 10 years (AVMA).
Cat life stages
The 2021 AAHA/AAFP guidelines name four age stages: kitten (birth up to 1 year), young adult (1 to 6 years), mature adult (7 to 10 years) and senior (over 10 years), plus an end-of-life stage that can come at any age. They say these are not absolutes (AAHA/AAFP).
What this can't tell you
These are guides, not medical advice. How your own pet is aging is a question for your vet.
Sources
- Wang et al., Quantitative Translation of Dog-to-Human Aging, Cell Systems 2020 (checked October 29, 2026)
- International Cat Care: cat life stages and age chart (checked October 29, 2026)
- AAHA: 2019 Canine Life Stage Definitions (checked October 29, 2026)
- 2021 AAHA/AAFP Feline Life Stage Guidelines (checked October 29, 2026)
- AVMA: Caring for senior cats and dogs (checked October 29, 2026)