Dog & Cat Age Calculator
Convert your dog or cat's age to human years — a size-based vet model plus the 2019 epigenetic formula. No more 'multiply by 7'.
Your companion is about 39 in human years.
※ Cats use the international 15-9-4 rule; dogs use the AKC/AVMA size-based chart (or the 2019 Wang et al. epigenetic formula). Results vary by breed and health and are for fun/reference. The "age × 7" rule is inaccurate.
🔒 Everything is calculated in your browser; nothing is sent to a server.
Why 'multiply by 7' is a myth
The old 'one dog year equals seven human years' rule has no scientific basis. Dogs mature very fast in their first two years — reaching roughly 15 human years by age 1 and about 24 by age 2 — then age more slowly. Body size matters too: large and giant breeds age faster and live shorter lives than small dogs. Multiplying by 7 badly misjudges both puppies and senior dogs, which is why veterinary groups use a size-adjusted curve instead.
Size-based conversion (AKC/AVMA)
This tool's default model follows the AKC/AVMA size-adjusted guideline. Dogs are grouped by weight: small (≤9 kg), medium (10–22 kg), large (23–40 kg), and giant (>40 kg). Every dog reaches about 15 human years at age 1 and 24 at age 2. After that, each dog year adds roughly 4 human years for small breeds, 5 for medium, 6 for large, and 7 for giant. So a 5-year-old medium dog is 24 + 3×5 = 39, while a 12-year-old giant is 24 + 10×7 = 94. Just pick the size group that matches your dog's weight.
The 2019 epigenetic clock (alternative)
A 2019 UC San Diego study (Wang et al., Cell Systems) compared DNA methylation in dogs and humans and proposed human_age = 16 × ln(dog_age) + 31, where ln is the natural logarithm. It gives about 42 human years at age 2, 57 at age 5, and 68 at age 10 — a curve that slows with age. Because it was built from 104 Labrador Retrievers, it ignores breed size and fits poorly below age 1, so we offer it as an optional model you can compare against the size chart.
Cats and the honest limits
Cats use one rule regardless of breed — the AAHA/AAFP/International Cat Care '15-9-4' rule: 15 human years in year one, 9 more in year two (24 total), then 4 per year. So a 5-year-old cat is 36 and a 10-year-old is 56. Whatever the species, these numbers are population averages, not a health diagnosis. Real aging depends on breed, weight, neutering, and lifestyle — ask your vet if you're concerned. Everything is computed in your browser; nothing about your pet is ever uploaded.
Frequently asked questions
Is one dog year really seven human years?
No — the ×7 rule is a myth. Dogs reach about 15 human years by age 1 and 24 by age 2, then age more slowly, and the rate depends on body size. Multiplying by 7 misjudges both puppies and older dogs.
How do I pick my dog's size?
Use body weight: small is about 9 kg or less, medium 10–22 kg, large 23–40 kg, and giant over 40 kg. For example, a Chihuahua is small, a Labrador is large, and a Great Dane is giant.
Which is right — the size chart or the epigenetic formula?
Both are evidence-based estimates. The AKC/AVMA size chart reflects breed size; the 2019 epigenetic formula is based on DNA changes but comes from Labradors only and ignores size. This tool defaults to the size chart and lets you switch models to compare.
Is this a medical diagnosis?
No. These are averages for planning and fun, not a diagnosis. Real aging varies with breed, weight, neutering, and environment — consult your veterinarian for any health concern. Your inputs stay in your browser and are never uploaded.