Glossary

Resting energy requirement

The calories a resting cat uses each day, a baseline vets multiply by a factor to work out how much food an individual cat needs.

Also called: RER, calorie needs, daily calories, maintenance energy requirement

The resting energy requirement, or RER, is the energy a cat needs to keep its body running while it is resting in a comfortable environment: breathing, circulating blood and keeping warm. A common formula is 70 times the body weight in kilograms raised to the power of 0.75. For a 4 kg cat that gives about 200 kilocalories a day.

RER is a starting point, not a feeding amount. Vets multiply it by a factor for the cat's situation. A neutered adult cat typically needs a little more than RER, an unneutered cat or an active one somewhat more, kittens a good deal more, and cats on a weight-loss plan fewer. The right figure depends on the individual, and it is adjusted after weighing the cat every few weeks.

To use this, check the calorie content of the food, usually listed on the pack as kcal per cup, can or kilogram, and divide the daily calories among meals. Include treats, which should be a small share of the day. Do not work out a weight-loss plan alone, because cutting calories too fast can harm a cat. Ask your vet to calculate it and to track the cat's weight.

Last reviewed November 7, 2026

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Related terms

Meal feeding Feeding a cat measured portions at set times each day instead of leaving food out, which helps control weight and spot appetite changes. Free feeding Leaving food out all day so a cat can eat when it likes, which suits some cats but often leads to overeating. Adult cat A fully grown cat, roughly from two to six years old, in its prime and needing steady care, exercise and a weight-controlled diet. Senior diet Food marketed for older cats, which varies widely, so the right choice depends on the individual cat's weight, teeth and health. Kitten food A food with more energy, protein, fat and minerals than adult food, made to support a kitten's fast growth.