Use the free Cat Calorie Calculator below, right in your browser. No sign-up, no software to install, and nothing is sent to a server.
How many calories does a cat need? The answer depends on weight, age, neutering, and activity, which is why two cats on the same food can need very different portions. The Cat Calorie Calculator turns those factors into two numbers vets actually use: RER, the resting energy need, and MER, the daily maintenance need.
RER is the energy a cat burns at rest in a warm room, doing nothing at all. It is calculated from body weight with the formula 70 times weight in kilos to the power of 0.75. That power matters: a cat twice as heavy does not need twice the calories, because larger bodies are more efficient per kilo.
MER is RER multiplied by a lifestyle factor. A neutered adult uses 1.2, an intact adult 1.4, a kitten 2.5, and a very active adult up to 1.6. A cat on a weight loss plan uses 0.8, which is a gentle deficit, not a crash diet. Pick the closest type in the tool and it does the multiplication for you.
Try the default example. A 4 kilo neutered adult has an RER of about 198 kcal per day and an MER of about 238 kcal per day. That is the whole daily budget, including treats. If treats give 30 kcal, the food bowl should give about 208, not 238 on top of treats.
Food labels make the next step easy once you know the target. A dry food at 380 kcal per 100 grams gives 238 kcal in about 63 grams. A wet food at 80 kcal per 100 grams gives the same energy in about 298 grams. Weigh food in grams with a kitchen scale, because scoops and cups vary by 20 percent or more.
Treats are the most common reason a cat gains weight on a measured diet. One small treat can carry 10 to 20 kcal, and five treats a day can add a tenth of the whole budget. Keep treats under a tenth of daily calories, count them in the total, and use part of the daily food allowance as play rewards instead.
Adjust slowly and watch the scale, not the bowl. If weight rises over a month, cut the total by 10 percent and re-check in four weeks. If weight falls when it should not, add 10 percent. Big sudden cuts backfire: hungry cats beg more, steal food, and lose muscle along with fat, which lowers their calorie need further.
Kittens, pregnant cats, and nursing mothers are exceptions to the adult rules, and their factors are higher for good reason. Growing and nursing bodies build tissue and milk, so they need far more energy per kilo than a resting adult. Use the kitten factor under one year, and ask a vet for pregnancy and nursing targets rather than guessing.
Illness changes everything, so this tool never replaces vet advice. Thyroid disease raises calorie needs, kidney disease and dental pain lower intake, and diabetes needs a vet led plan. If your cat is losing weight without trying, gaining fast, drinking much more, or eating far less, book a vet visit before changing portions.
Start with the number, measure the food, and re-weigh monthly. Calories are a starting point, not a verdict: the scale and the body condition score over the next month tell you whether the number is right for your cat. Small, steady adjustments beat one big change every time.
A kitchen scale is the one purchase that makes every calorie number real. Weighing food takes ten seconds and removes the largest error in home feeding, which is the scoop. Scales also help with treats: weigh a day treats once, learn what they look like, and you can portion them by eye afterwards with far less error. If you feed wet food, weigh the pouch portion too, since half a pouch is easy to misjudge. Accurate grams turn the calculator result from a guess into a plan you can actually follow.
Versión en español: Calculadora de calorías para gatos – Necesidad diaria según peso