About Cat Calculators

Free, accurate, vet-informed calculators for every stage of your cat’s life — built by a cat owner who got tired of searching for simple answers.

Why I Built This Site

“I just wanted to know how many calories my cat needed. It took me an hour and four different websites to get a clear answer.”

My name is Olivia Smith. I have kept cats my whole life — right now I share my home with two, a tabby named Biscuit and a senior tortoiseshell called Mabel who is eleven and requires considerably more looking after than she did a few years ago.

A few years ago I found myself in a frustrating situation. Mabel had started losing a little weight and I wanted to understand her calorie needs better. I looked online and found either extremely technical veterinary literature that required a science degree to follow, or breezy blog posts that gave the same generic numbers regardless of the cat’s weight, age, or diet.

I knew the RER formula existed. I knew that a senior cat on wet food had completely different water and calorie needs from a kitten on dry kibble. But nowhere could I find a single calculator that took all of that into account and gave me a real number I could actually use.

So I decided to build it myself. And then one calculator became two, and two became eight, and somewhere along the way Cat Calculators became a proper resource.

Every calculator on this site started as a question I had about one of my own cats. Every piece of content is written the way I wish someone had explained it to me: in plain English, based on real veterinary sources, without padding or waffle.

What Makes Our Calculators Different

Most cat calculators online give you a number and nothing else. We build ours to actually explain the result so you understand what it means and what to do with it.

Every calculator on this site uses verified veterinary formulas. The calorie calculators use the RER formula endorsed by the WSAVA and the American College of Veterinary Nutrition. The pregnancy calculator uses the 63 to 65 day gestation standard cited by PetMD and reviewed veterinarians. The growth calculator uses the 16-week landmark validated by WALTHAM across thousands of domestic cats.

We do not make up numbers. We do not average things out and round to the nearest ten. We cite our sources on every calculator page so you can check the underlying science yourself.

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Vet-standard formulas
Every calculation uses the same methodology found in clinical veterinary nutrition guides — RER, MER multipliers, BCS scales, and AAHA life stage classifications.
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Cited sources
Every calculator page includes an expandable references section listing the peer-reviewed papers, veterinary guidelines, and institutional sources behind the numbers.
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Human-written content
All content is written by real people who have actual cats and read the veterinary literature. We aim for the standard of a well-informed friend, not a textbook.
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Regularly reviewed
We update calculators and content when veterinary guidelines change. Formulas and life stage classifications are checked against current WSAVA and AAHA standards.

Our Calculators

Cat Calculators covers the full range of practical questions cat owners ask — from “how old is my cat in human years” to “how much should I feed my senior CKD cat on a wet diet.” Here is what is currently live on the site.

🕐 Cat Age Calculator
🍽️ Cat Food Calculator
🔥 Cat Calorie Calculator
💧 Cat Water Calculator
🐣 Cat Pregnancy Calculator
⚖️ Cat BMI Calculator
📈 Cat Growth Calculator
💊 Medication Calculators
More coming

Meet the People Behind Cat Calculators
This site is run by two people: a cat owner who builds and writes the content, and an editor who reviews it for accuracy and clarity.
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Olivia Smith
Founder, Cat Care Specialist & Primary Author

Olivia is a lifelong cat keeper and the founder of Cat Calculators. She has lived with cats for over fifteen years and currently cares for two: Biscuit, a four-year-old tabby, and Mabel, an eleven-year-old tortoiseshell managing early-stage kidney disease.

Her interest in cat health calculations started from personal necessity. Caring for a senior cat with CKD pushed her to understand the veterinary science behind hydration, calorie restriction, and dietary phosphorus in a practical way. She found the existing online tools too generic to be genuinely useful, which led directly to building this site.

Olivia researches every calculator from primary veterinary sources — WSAVA guidelines, AAHA life stage standards, Cornell Feline Health Center publications, and peer-reviewed nutrition literature. She writes all content on this site and tests every calculator against real scenarios before publishing.

She is not a licensed veterinarian. She is an experienced, well-informed cat owner who treats the veterinary literature seriously and presents it in a way that other cat owners can actually use. All health-critical content is reviewed by an editor and carries a disclaimer encouraging readers to consult their vet for individual advice.

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Adam Erwin
Editor & Content Reviewer

Adam serves as the editorial reviewer for Cat Calculators. He reviews all calculator logic and content for accuracy, clarity, and consistency before publication. His role is to catch errors, question assumptions, and make sure the information we publish is clearly explained and correctly sourced.

He brings a background in science communication and has worked with health and wellness content across several websites. He believes that accurate health information should be accessible to everyone — and that cat owners deserve better than generic advice copied from food packaging.

Our commitment to accuracy

All calculator formulas are based on published veterinary guidelines from organisations including the WSAVA, AAHA, AVMA, and Cornell Feline Health Center.
Every calculator page includes a source references section so you can verify the underlying science independently.
We clearly distinguish between established veterinary formulas and general estimates, and we note when individual variation means the calculator result is a starting point rather than a precise prescription.
We are not a licensed veterinary practice and do not provide personalised medical advice. All content is intended as general information for educational purposes. Always consult a qualified vet for your individual cat’s health needs.
If you find an error or have a suggestion for improving any calculator, please contact us at Olivia.catcalculators@gmail.com