Pet Age Calculator
Save your dogs and cats and watch their age in human years count up live from their birthday.
Loading your pets…
Your pets are saved only in this browser (no account, nothing uploaded). Human-age estimates use a common approximation and vary by breed and health.
Use on any page (bookmarklet)
Want Pet Age Calculator without leaving the page you're on? Drag the button below to your bookmarks bar, then click it on any website to open Pet Age Calculator right there — it runs entirely in your browser.
Use responsibly: a bookmarklet runs on whatever page you click it on. Avoid sensitive sites such as online banking, payment, or healthcare pages — you run it at your own risk. Everything is processed locally and no data is sent anywhere. See our Terms.
- Show your bookmarks bar if it's hidden — Ctrl+Shift+B (⌘+Shift+B on Mac).
- Drag the button above onto the bookmarks bar.
- Open any website and click the bookmark — the Pet Age Calculator panel appears in the top-right corner. Use ✛ to move it between corners, or ›/‹ to tuck it against the edge and pull it back out.
- Click the bookmark again (or the ✕) to close it.
Note: a few sites with strict security policies may block bookmarklets.
Examples
2-year-old medium dog
Input
Dog · 2 years · Medium
Output
≈ 24 human years — Young adult
5-year-old large dog
Input
Dog · 5 years · Large
Output
≈ 42 human years — Adult
3-year-old cat
Input
Cat · 3 years
Output
≈ 28 human years — Young adult
About this tool
This free pet age calculator converts your dog or cat's age into human years using a modern, stage-based formula instead of the outdated “multiply by 7” rule. Pets grow up fast in their first two years and then age at a pace that depends on species and, for dogs, size — so this tool asks for all three to give a closer estimate.
How to use
- Give your pet a name and choose dog or cat (and a size for dogs).
- Enter its birthday — or switch to Age and enter years and months.
- Press Add pet to save it. Add as many pets as you like.
- Each saved pet shows its human-equivalent age and life stage, plus a live counter of days, hours, minutes, and seconds since it was born.
A guide, not a diagnosis
The numbers are averages across many breeds. Your pet's real aging depends on breed, weight, and overall health, so use this as a fun reference and talk to your vet for anything health-related.
Frequently asked questions
How is a dog's age in human years calculated?
This tool uses a widely used approximation: the first year of a dog's life is about 15 human years, the second year adds about 9 (so a 2-year-old dog is roughly 24), and each year after that adds 4–6 human years depending on size — smaller dogs age more slowly, larger dogs faster.
Is the old 'multiply by 7' rule accurate?
No — the classic '1 dog year = 7 human years' rule is far too rough. Dogs mature very quickly in their first two years and then age at a rate that depends on their size, which is why this calculator uses a size-aware, stage-based formula instead.
How does cat age work?
Cats follow a similar curve: about 15 human years for the first year, roughly 24 by age two, then about 4 human years for each additional year. Size isn't used for cats.
Why does dog size change the result?
Smaller dog breeds tend to live longer and age more slowly in later life, while large and giant breeds age faster. Selecting Small, Medium, or Large adjusts the per-year rate after age two to reflect that.
Can I enter months for a puppy or kitten?
Yes. Enter the years and the extra months, and the calculator converts the total to a decimal age — useful for young pets where a few months make a big difference in the early, fast-aging period.
Can I save my pets and watch their age count up?
Yes. Add each pet with a name and its birthday (or age), and it's saved in your browser. Every saved pet shows a live counter — days, hours, minutes, and seconds since birth — alongside its human-equivalent age and life stage, so you can watch it tick up in real time.
I don't know the exact birthday — can I still use it?
Yes. Switch the entry to 'Age (yr / mo)' and enter roughly how old your pet is. The tool sets an approximate birthday from that so the live counter and human age still work; you can edit it later if you learn the real date.
Is this a medical tool?
No, it's a fun estimate based on population averages. Real aging depends on breed, weight, diet, and health. For anything about your pet's health, ask your veterinarian.
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