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Dog and cat age calculator

Convert a dog’s or cat’s age into human years, with a life stage for each result.

Input
Output
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Dog and cat age calculator
Paste one or more ages, one per line, and this tool converts each into its human-year equivalent — useful for a quick sanity check on how old a pet really is, comparing pets of different sizes, or just settling a dinner-table argument about whether your dog is "basically a teenager."
Pick the species first: dog or cat. For dogs, the breed size category (small, medium, large or giant) changes the result once the classic model passes the shared first two years, because larger dogs age faster in their later years than small ones. The calculation model chooses between the classic, widely used table (15 human years for year one, 9 more for year two, then a flat rate per year after) and an epigenetic model — a logarithmic curve in the shape popularized by recent epigenetic-clock research on dogs, applied here to both species for consistency. Turn on the reverse option to go the other way: enter a human age and get the equivalent pet age instead. Paste a whole list to convert several ages at once, and switch the output to a table when you want the results lined up in columns instead of one sentence per line.
Ages can be entered as whole years ("7"), years and months ("3 6" or "3y 6m"), or a decimal ("3.5" is read as 3 years 6 months). Anything that cannot be read as a plausible age is marked instead of stopping the whole batch, so one typo in a long list does not lose the rest of the results. Each entry also comes with a life stage — baby, young adult, adult or senior — worked out from the computed human-equivalent age.
Everything runs in your browser: no age, breed or species is ever sent anywhere. Copy the result, download it as a .txt file, or send it straight back into the input to try another model or direction.
FAQ
Which model is more accurate, classic or epigenetic?
Neither is exact — there is no single scientific standard for converting pet age to human years. The classic table is the long-standing rule of thumb; the epigenetic model reflects newer research (on dogs) into a smoother curve. Both are estimates, not veterinary advice.
Why does breed size only matter for dogs?
Aging speed varies a lot with adult body size in dogs — small breeds tend to live longer and age more slowly in their later years than giant breeds. Cats do not have an equivalent standardized size-based chart, so the calculator uses one rate for every cat.
How do years and months work in the input?
Enter a whole year ("5"), a year plus months ("5 6" or "5y 6m"), or a decimal ("5.5"), which is read as 5 years and 6 months. Each line is converted independently.
What does the reverse option do?
It flips the calculation: instead of entering the pet’s age, you enter a human age and the tool returns the equivalent age for that species, size and model.
Is my pet’s data uploaded anywhere?
No. The conversion runs entirely in your browser — nothing you type is sent to a server.