Compare a dog and a cat by age
Two species, two completely different aging curves, side by side. The answer to "wait, is my cat actually older than my dog?" — often yes, sometimes no, always interesting.
Dog Your dog
Cat Your cat
What the numbers mean
Dogs and cats both age fast in their first two years (~15 + 9 human-equivalent years), then settle into different per-year rates. Cats slow down predictably to about 4 human years per cat year. Dogs slow at different rates depending on body size — 4 per year for small breeds, up to 7 per year for giant breeds.
That's why a 6-year-old Yorkie and a 5-year-old indoor cat are nearly the same age in human terms (around 40), but a 6-year-old Great Dane is already 52 in human years. Size is the dominant lifespan variable for dogs; lifestyle is the dominant variable for cats.
Common surprises
- Your cat is probably older than you think. An 11-year-old indoor cat is ~60 in human years — a senior, despite still acting like a "young" pet.
- Giant dogs catch up fast. A 7-year-old Great Dane is older in human terms than a 14-year-old Chihuahua.
- Outdoor cat lifespan is grim. A 6-year-old outdoor-only cat is at the median of its expected lifespan.
- Small dogs and cats track each other closely. Yorkies and indoor cats reach senior status around the same calendar age (10–11 years).
Cross-species age FAQ
Why compare a dog and a cat?
Most multi-pet households have both. Cats and dogs age along very different curves — small dogs and indoor cats both live 13–18 years; large dogs live half as long; outdoor cats half again as long. The cross-species comparison surfaces the surprising answer to "which of my pets is actually older in human terms?"
Can a 12-year-old cat be younger than a 7-year-old dog in human terms?
Yes — and it happens routinely with large or giant dog breeds. A 7-year-old Great Dane is roughly 59 in human years, while a 12-year-old indoor cat is roughly 64. So they're close, with the cat slightly older. Switch the dog to a small Yorkie at 12 years old and the gap inverts.
Which method does each species use?
Dogs use the AKC size-based formula (different aging rates for small, medium, large, giant breeds). Cats use the AAFP/AAHA Feline Life Stage formula (4 human years per cat year after age 2). Both are the most-cited references for their species.
Can I save my comparison?
Your individual pets save automatically via the calculator pages. The comparison itself isn't stored, but you can copy the result to the clipboard for sharing, or print it for a vet visit.
My dog and cat are basically the same age in human terms — what does that mean?
Practically nothing for their behaviour, but emotionally a lot for households. Pets often share life-stage transitions together — they enter senior stage around the same calendar age, even if they're different ages on paper.