Pet Age Calculator
The old "1 pet year = 7 human years" rule is a debunked myth (the AVMA calls it an "old myth") — it treats every year the same, but pets age fastest in their first two years, then level off. The modern method: year 1 ≈ 15 human years, year 2 adds ≈9 more (24 total), then each year after adds 4-7 more depending on species and, for dogs, breed size — bigger dogs age faster in their later years. Skipping breed size is the single biggest source of inaccurate results, which is why most simple calculators get this wrong.
Convert your dog or cat's age to human years using the modern vet-recommended method — not the outdated "times 7" myth.
How it works
- Pick your pet's species — and for dogs, their breed size, since that changes how fast they age after year two
- Enter their age in years (decimals like 0.5 work for puppies and kittens)
- See their age in human years side by side with the old, debunked "×7 rule" so you can see how much it's off by
Frequently asked questions
Is the "1 dog year = 7 human years" rule accurate?
No. The American Veterinary Medical Association explicitly calls this an "old myth." It treats every year the same, but pets actually age fastest in their first two years and then level off — a straight ×7 multiplier overstates a young pet's age and understates an older pet's age.
Why does breed size matter for dogs?
After the first two years, larger dogs age faster than smaller ones. A giant-breed dog and a toy-breed dog that are both 5 years old are not biologically the same age — skipping breed size is the single most common reason dog age calculators give inaccurate results.
Does breed size matter for cats?
No — cats don't have the same size-based aging spread that dogs do, so this calculator only asks for breed size when you pick "Dog."
Where does the modern formula come from?
It follows the widely-cited veterinary approximation: a pet's first year is about 15 human years, the second year adds about 9 more (24 total), and each year after that adds roughly 4-7 more years depending on species and, for dogs, breed size.
Related tools
From the blog
Update history
- 2026-09-03 The species toggle now shows a dog/cat icon for each option.
- 2026-09-02 Launched: pet age calculator using the modern vet-recommended (non-linear, breed-size-aware) method, shown side by side with the outdated "×7 rule" for comparison. Entirely client-side.