Tools
Five calculators for the questions every cat owner ends up asking.
Each one uses the formulas in published veterinary nutrition and life-stage guidance, works in metric, runs entirely in your browser and remembers your answers on your own device. None of them needs an account, and none of them replaces your vet.
Reviewed September 2026
The order that makes sense
- 1Weigh the cat properly firstStand on the scales holding the cat, then alone, and subtract. Everything else on this page depends on that number being real rather than remembered.
- 2Check the weight is rightThe ideal weight checker cross-references breed range against what you can feel over the ribs. Body condition wins where the two disagree.
- 3Turn the target into gramsThe portion calculator converts a calorie target into portions of the wet and dry food you actually buy, split across the meals you actually serve.
- 4Match the care to the life stageThe age converter says which stage your cat is in and what changes: screening frequency, diet, and the household adjustments an older cat needs.
- 5Re-weigh every two weeksAdjust by about ten per cent when the trend is going the wrong way. Slow and boring is the only safe speed for feline weight change.
What these tools are, and are not
Every calculation here comes from published veterinary guidance rather than a rule of thumb: resting energy requirement from body weight, life-stage multipliers for kittens, neutered adults and seniors, and the nine-point body condition scale used in clinics worldwide.
That gives an accurate starting point, not an individual prescription. Metabolism varies by around twenty per cent between cats of identical weight, so a calculated portion is a hypothesis you test on the scales over the following month.
Nothing you enter leaves your device. Values are kept in your browser's own storage so a tool reopens where you left it, and there is no account, no tracking of your cat's data and no email required.
Where a tool touches something clinical, weight loss you did not plan, a cat refusing food, straining in the tray, it says so and points you to a vet instead of a number.
Questions people actually ask
Are these cat calculators free?
Yes, all five are free, need no account and run entirely in your browser. Nothing you type is sent to a server; the numbers you enter stay on your own device so a tool reopens where you left it.
How accurate are cat calorie and weight calculators?
They use the same resting-energy formula and life-stage multipliers that veterinary nutrition guidelines use, so the starting figure is sound. Individual metabolism varies by roughly twenty per cent either way, which is why every tool here tells you to weigh the cat every two weeks and adjust rather than trust the first number.
Which tool should I start with?
If you already have a cat, start with the ideal weight checker: almost every feeding decision depends on whether the cat is at a healthy weight. Then use the portion calculator, which takes that target and turns it into grams of the food you actually buy.
Can these replace a vet?
No. They are planning aids that help you ask better questions and spot changes earlier. Anything involving weight loss you did not intend, refusal to eat, straining in the litter tray or a sudden behaviour change is a veterinary matter, not a calculator one.
Do the tools work on a phone?
They are built phone-first. The result panel stays visible while you change your answers, so you can adjust a figure and see the effect without scrolling, and every input is sized for thumbs rather than a mouse.
Do they use metric or imperial units?
Metric throughout, kilograms, grams and millilitres, because the site is written for an international readership. Any cost mentioned is an indicative EUR range that varies widely between countries.
How often are the tools reviewed?
Each tool names the guidance it was checked against and the month it was last reviewed, at the top of its page. When the underlying veterinary guidance changes, the formula and the date change with it.