Pet Age Calculator — Dog & Cat Years to Human Years
Convert your dog or cat’s age to human years — dogs by size class (small, medium, large) — with a full reference table. A rough guideline, right in your browser.
🔒 Runs entirely in your browser. Your input and output are never sent to a server or stored — fully private.
Rough guideline only: year 1 ≈ 15 human years, year 2 ≈ +9, then +4 (cat/small dog), +5 (medium) or +6 (large) per year. Individual pets vary widely — this is not veterinary advice.
About this tool
How old is your dog or cat in human terms, really? This converter uses modern veterinary rules of thumb instead of the outdated multiply-by-seven myth: cats follow a standard curve that reaches roughly 24 human years by age two and then slows, while dogs are converted by size class, because small breeds age far more gently in later life than giant ones. Pick the species, the size for dogs, and the age, and the human-equivalent figure appears instantly. The conversion runs entirely in your browser — nothing about you or your pet is collected or sent anywhere.
Frequently asked questions
Why is the old rule of thumb that 1 dog year equals 7 human years outdated?
Because pets do not age at a constant rate. Dogs and cats mature extremely fast at first — a one-year-old is roughly a human teenager, and by age two both species reach the equivalent of about 24 human years — then the pace slows sharply. Size matters too: a Chihuahua can live past 15 while a Great Dane is elderly at 7, so no single multiplier fits every dog. Modern charts therefore use a steep early curve followed by size-dependent yearly increments, which is exactly what this tool does.
How exactly are cat and dog ages converted here?
Cats follow the widely used veterinary curve: about 15 human years for the first year, 24 by year two, then roughly 4 human years for each cat year after that. Dogs use the same steep start, but the later increments depend on the size class you pick — small dogs add around 4 human years per year, medium and large dogs more, and giant breeds the most, reflecting their shorter lifespans. Your inputs are processed instantly on your device only; nothing is transmitted to any server.
Is this an accurate medical assessment of my pet's age?
No — it is a general guideline built on population averages, not veterinary advice. Individual aging varies enormously with breed, genetics, weight, diet, and dental and organ health, so two pets of the same age and size can be in very different biological shape. Use the result for perspective — understanding that your cat is a senior, say — but rely on your veterinarian to assess your own animal's condition and to guide age-related decisions such as screening tests, diet changes or senior care.