Pet Age Calculator

Features

• Cats and dogs use a body-size curve, not a blanket ×7
• Five sizes: cat, small, medium, large and giant dog
• Segmented rule: year 1 = 15, year 2 adds 9, then 4–6 per year
• Reports the life stage: young, junior, adult or senior
• Enter a birth date or an age, one per line, several at once
• A “simple ×7” mode is kept for comparison, to show the gap
• The basis of each conversion is spelled out for checking
• Computed locally; birthdays and ages are never uploaded

How to use

1. Pick the animal (a cat, or a dog of a given size)
2. Pick the method: body-size curve or simple ×7
3. Type a birth date (2020-05-01) or an age (3), one per line
4. Results appear at once and can be copied row by row or all at once

FAQ

Why can I not just multiply by 7?

Because pets do not age at a constant rate. Year one takes them to about 15 human years (sexual maturity), year two adds 9 to reach about 24, and only then does it slow. Multiplying a 2-year-old cat by 7 gives 14, when it is really close to 24 — a decade off.

Why split dogs by size?

Because ageing and lifespan differ enormously by size. After year two a small dog gains about 4 human years a year, a large dog about 6, and giants more. Two 8-year-old dogs come out near 48 human years if small and around 66 if giant.

Can a vet use this number?

No. Breed, genetics, size, diet and veterinary care can move an individual several years off the curve. It is a convenient way to talk about life stage, not a diagnosis.

Can I enter a birth date?

Yes. Give a date like 2020-05-01 and the tool works out the age in days first. Each line can hold either a date or an age, and you can mix them.