How many calories does a cat need per day? The answer depends on its weight, its age, and how active it is — and the way to work it out is resting energy requirement, or RER: RER equals 70 times body weight in kilograms to the power 0.75, and daily calories are RER multiplied by a factor for the cat's life stage. This guide is the cat calorie calculator in words: the formula, the factors, the worked examples, and how to use the result — including treats, weight loss, and weight gain. Every figure is an estimate, not a prescription: individual cats vary, and the vet's advice matters more than the formula. The cat calorie calculator does the same calculation for your cat's exact weight and stage.
The short version is: weigh your cat, work out its RER, multiply by the factor for its stage, and you have its daily calories. A neutered adult cat needs about 1.2 times RER, and an intact adult about 1.4 times. A kitten needs about 2.5 times RER. A senior needs less: about 1.2 to 1.4 times RER. The cat food calculator guide gives the same method with the food amounts in cups and grams, and the cat food portion calculator guide gives the portion sizes.
The cat calorie calculator formula
The formula is: RER equals 70 times body weight in kilograms to the power 0.75, and daily calories equal RER multiplied by a factor. The factor is about 1.6 for a neutered adult cat, about 1.8 for an intact adult cat, about 2.0 to 3.0 for an active cat, about 2.5 for a kitten, and about 1.2 to 1.4 for a senior. A lactating cat needs about 2 to 4 times RER, depending on the size of the litter.
| Body weight | Neutered indoor (x1.2) | Intact adult (x1.4) | Active cat (x1.5) | Senior / weight loss (x1.2) |
|---|---|---|---|---|
| 2 kg | 140 | 165 | 175 | 140 |
| 3 kg | 190 | 225 | 240 | 190 |
| 4 kg | 240 | 275 | 295 | 240 |
| 5 kg | 280 | 330 | 350 | 280 |
| 6 kg | 320 | 375 | 405 | 320 |
| 8 kg | 400 | 465 | 500 | 400 |
Read the table from top to bottom and the pattern is clear: a cat's calorie needs rise with weight, but not in proportion — a cat that is twice as heavy does not need twice as many calories, because RER grows with weight to the power 0.75. A 5 kg cat needs about 280 kcal a day as a neutered adult, a 10 kg cat needs about 470 kcal, and a 20 kg cat needs about 795 kcal. The cat calorie calculator works out the exact figure for any weight and stage.
Worked examples
A 4 kg neutered indoor cat: RER is 70 times 4 to the power 0.75, which is about 198 kcal, and daily calories are 198 times 1.2, which is about 237 kcal a day. A 6 kg neutered indoor cat: RER is about 268 kcal, and daily calories are about 322 kcal a day. A 3 kg neutered indoor cat: RER is about 160 kcal, and daily calories are about 192 kcal a day.
To work out your own cat's needs, weigh it, look up its RER in the table above, and multiply by the factor for its stage. If your cat is between two weights in the table, take the nearer one — the formula is an estimate, and a few percent either way does not change the result much. The how much food should a kitten eat guide gives the calorie tables for young cats, and the senior cat diet guide covers feeding in the senior years.
Treats, weight loss, and weight gain
Treats count: a treat is food, and it counts towards the daily calories. A good rule is that treats should be no more than a tenth of the daily calories — so a cat that needs 630 kcal a day should get no more than about 63 kcal of treats, and a cat that needs 237 kcal a day should get no more than about 24 kcal of treats. A biscuit, a chew, and a handful of training treats add up fast, and a cat that gets a lot of treats needs less of its main food, or it will gain weight.
For weight loss, feed for the target weight, not the current weight: work out RER at the target weight, multiply by about 1.0, and aim to lose about 1 percent of body weight per month for a dog and about 0.5 to 1 percent per month for a cat. For weight gain, increase the food by about a tenth and re-check in two weeks. A cat that is losing weight on the calculated amount needs more food, and a cat that is gaining weight needs less — the scales and the body condition score matter more than the formula. The cat weight loss diet plan guide covers a cat that needs to lose weight, and the how to help a cat gain weight safely guide covers a cat that needs to gain weight.
When the calculator is wrong
The calculator is wrong when the cat's weight is wrong, when the factor is wrong, or when the food's calories are wrong. Weigh your cat every month, and re-check the amount every two weeks as a young animal grows. Use the right factor: a neutered adult needs less than an intact adult, a senior needs less than a young adult, and a very active cat needs more than a couch potato. Check the bag for the food's calories, and weigh the food — do not guess with a cup.
The calculator is also wrong when the cat is ill, pregnant, nursing, or recovering from surgery: a pregnant cat needs more food in the last weeks, a nursing cat needs much more, and a sick cat may need a special diet. A cat that is losing weight on the calculated amount needs more food, and a cat that is gaining weight needs less — the scales and the body condition score matter more than the formula. The feeding a pregnant cat guide covers feeding in pregnancy, and the feeding a nursing cat guide covers feeding while nursing.
How to use the calculator
Use the calculator to get a starting point, then adjust by the scales and by feel: weigh your cat every month, feel its ribs and waist, and keep it at a body condition score of 4 or 5 out of 9. If your cat is gaining weight, reduce the food by a tenth and re-check in a month. If it is losing weight, increase the food by a tenth and re-check in a month. A cat that is at a healthy weight, eating a measured amount, and exercised every day, is a cat that will live longer and feel better.
Use the calculator to check the bag, too: if the bag says to feed much more than the calculator says, the bag is probably wrong for your cat — feeding guides on bags are often generous, because they are written for active cats and because the maker wants you to buy more food. Trust the calculator, the scales, and your vet, not the bag. The cat calorie calculator works out the exact figure for any weight and stage, and the cat food calculator guide gives the same method with the food amounts in cups and grams.
For related reading, see the cat calorie calculator, the cat food calculator guide, the cat food portion calculator guide, the how much food should a kitten eat guide, the senior cat diet guide, the cat weight loss diet plan guide.
Frequently asked questions
How many calories does a cat need per day?
It depends on its weight, its age, and how active it is. Work out its RER — 70 times body weight in kilograms to the power 0.75 — and multiply by a factor: about 1.2 for a neutered indoor cat, 1.4 for an intact adult, 1.4 to 1.6 for an active cat, 2.5 for a kitten, and 1.1 to 1.4 for a senior. The table above gives the figures by weight.
What is RER?
RER is resting energy requirement: the calories a cat needs at rest, in a comfortable temperature, doing nothing. It is 70 times body weight in kilograms to the power 0.75. Daily calories are RER multiplied by a factor for the cat's life stage — about 1.6 for a neutered adult dog, or 1.2 for a neutered indoor cat.
How many calories should a 10 kg cat eat?
A 10 kg neutered indoor cat needs about 472 kcal a day. A 10 kg cat is very large, though — most cats weigh 3 to 6 kg. Check the bag for the food's calories, and weigh the food.
Do treats count towards daily calories?
Yes — a treat is food, and it counts. Treats should be no more than a tenth of the daily calories. A biscuit, a chew, and a handful of training treats add up fast, and a cat that gets a lot of treats needs less of its main food, or it will gain weight.
How many calories does a cat need to lose weight?
Feed for the target weight, not the current weight: work out RER at the target weight, multiply by about 1.0, and aim to lose about 1 percent of body weight per month for a dog and about 0.5 to 1 percent per month for a cat. Weigh your cat every month, and adjust the food by a tenth at a time.
When should I ask a vet about calories?
Ask your vet if your cat is losing or gaining weight on the calculated amount, if it is pregnant, nursing, ill, or recovering from surgery, or if it has a health condition that affects its diet. A vet can work out the exact amount for your individual cat, and can advise on a special diet if it needs one.
Results on this page are estimates for general information only and are not veterinary advice. If your pet is ill, underweight, overweight, pregnant, or has a health condition, consult your veterinarian before changing diet or care.