About PetCalc
PetCalc is a small, independent site that answers the practical questions dog and cat owners actually search for: how old is my pet in human years, how much should I be feeding, when is the next vaccine due, how big will this puppy get. No signup, no paywall, and nothing to install.
Why the site exists
Most of these questions have a real answer that vets use every day — and most of the internet answers them with a myth. The “one dog year equals seven human years” rule is the obvious example: it has been wrong for decades and it is still the first thing most people are told.
Every tool here exists because the honest answer is a short calculation, and there was no reason for anyone to pay for it or wade through ten pages of filler to find it.
Where our numbers come from
Our calculators are built on published veterinary standards rather than rules of thumb:
- Feeding calculators use the resting energy requirement formula — RER = 70 × (body weight in kg)0.75 — multiplied by the life-stage factors used in veterinary nutrition guidance.
- Age calculators follow the modern tiered model (year one ≈ 15 human years, year two adds 9, then 4–7 a year by size for dogs and a steady 4 for cats) rather than the seven-year myth.
- The vaccination schedule follows the AAHA canine vaccination guidelines, including the second doses that lifestyle vaccines need.
- Growth and lifespan data are checked against breed-level records rather than a single source.
How we keep it consistent
A calculator and an article that disagree are worse than neither, so the numbers behind our tools live in one shared place and every chart on the site is generated from it. When guidance changes, or when we find an error, we fix the tool and every page that quotes it in the same pass.
We audit the whole site for contradictions periodically — matching formulas, health thresholds and figures across every page — because on a site about animal health, two different answers are a real problem.
What we are not
PetCalc is not a veterinary service and does not give medical advice. Our tools produce estimates based on averages, and your pet is not an average. Genetics, health conditions, medication and lifestyle all change the real answer.
Anything urgent — a pet that has stopped eating, sudden weight loss, difficulty breathing, a suspected poisoning, or a problem during labour — belongs with a vet immediately, not with a calculator. We say so on the pages where it matters, and we deliberately do not publish medication doses.
Your privacy
Everything you type into a calculator is processed in your browser. We do not store it, send it anywhere, or ask you to create an account. We use privacy-respecting analytics to see which pages are useful, which is explained in full in our privacy policy.
How the site is funded
PetCalc is supported by display advertising. Ads never influence what our calculators say or what our guides recommend, and we do not accept payment to feature a brand or product inside our content.
Found a mistake?
Tell us. Corrections are the fastest way this site gets better, and we would rather be corrected than be confidently wrong about something that affects an animal. Contact us with the page and what looks off — we read every message and fix real errors quickly.