Daily calories for a cat, worked out properly

A cat's daily calorie need is smaller than most owners think. A typical 4.5-kilogram neutered adult cat needs only about 260 kcal a day — roughly the calories in a small can of wet food plus a handful of kibble. That is because cats are small, and because the resting energy requirement scales with weight to the power of 0.75, so a cat needs far fewer calories per kilogram than a dog of the same weight would. The formula is RER = 70 × (body weight in kg)^0.75, and for a 4.5-kilogram cat the RER is about 218 kcal. Multiply by the activity factor — 1.2 for a neutered adult, 1.4 for an intact adult, 2.5 for a kitten under four months, 2.0 for an older kitten, 1.0 for an inactive or senior cat and 0.8 for a vet-guided weight-loss plan — and you have the daily figure. This calculator shows the RER, the factor and the result, plus a table of every life stage at your cat's weight, so you can see how much the number moves.

The table matters because the range is wide. The same 4.5-kilogram cat needs about 545 kcal a day as a young kitten, 436 as an older kitten, 305 as an intact adult, 262 as a neutered adult, 218 as a senior and 174 on a weight-loss plan. That is a threefold difference between a kitten and a cat on a diet, at the same weight. It explains why kittens seem permanently hungry and why neutered adult cats gain weight so easily if their food is not reduced after neutering. It also explains why the feeding guide on the bag — written for an average cat — is often wrong for your cat: if your cat is a neutered indoor senior and the bag guide assumes an active intact adult, the guide can overfeed by fifty percent or more.

How to use the number

Divide the daily calories by the kcal per can or per cup on your food's label to get the daily amount, and measure it — do not eyeball it, and do not leave the bowl always full. Take ten percent of the daily figure for the treat budget: for a cat needing 260 kcal a day, that is 26 kcal of treats, which is about two or three small treats. Then monitor for two to four weeks: weigh your cat, feel the ribs, and look at the waist. At an ideal body condition (BCS 5) you can feel the ribs under a thin layer of fat and see a waist from above. If your cat is gaining, cut the food by about ten percent; if losing, add ten percent. Change one thing at a time and give it time — a cat's weight responds slowly, and frequent changes tell you nothing.

What affects the result

Neutering is the single biggest change in a cat's calorie needs: it drops the factor from 1.4 to 1.2, and the risk of weight gain is highest in the months immediately after the operation. Age is next: kittens need two to two and a half times their RER, while seniors need about their RER. Activity matters less for cats than dogs, but an indoor cat that never plays needs fewer calories than one that roams and hunts. Weight matters, but be careful — if your cat is overweight, use the target weight your vet has set, not the current weight, or you will feed to maintain the overweight. Illness changes everything: cats with kidney disease, diabetes, hyperthyroidism or urinary problems need diets and calorie levels set by their vet, and this calculator is not a substitute.

Common mistakes

Free-feeding dry food is the biggest mistake — a bowl that is always full is an open invitation to overeat, and most cats will take it. The second is the bag guide, which is a generous range for an average cat. The third is treats: a few treats a day can be a quarter of a small cat's intake, because the total is so small. The fourth is cutting food sharply to make a fat cat lose weight — rapid weight loss in cats can cause hepatic lipidosis, fatty liver disease, which is life-threatening. A cat should never lose more than about one percent of body weight per week, and any weight-loss plan must be vet-supervised. The fifth is feeding dog food, which lacks the taurine and vitamin A a cat needs and will cause serious deficiency within weeks.

When to see a vet

See your vet before changing your cat's calories if it is overweight, has kidney disease, diabetes, urinary problems or hyperthyroidism, or is a kitten, pregnant or nursing. See a vet urgently if your cat stops eating for more than a day — a cat that does not eat for twenty-four to forty-eight hours is at risk of fatty liver disease. Use the cat food calculator to turn calories into cups and grams, the cat ideal weight calculator to find the target weight, and the treat calorie calculator to work out the treat budget.