How much food does a dog need? 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 dog's life stage. This guide is the dog food calculator in words: the formula, the factors, the worked examples, and the cups and grams — so you can work out how much your dog needs without guessing. Every figure is an estimate, not a prescription: individual dogs vary, and the vet's advice matters more than the formula. The dog food calculator does the same calculation for your dog's exact weight and stage.
The short version is: weigh your dog, work out its RER, multiply by the factor for its stage, and divide the result by the calories in its food. A neutered adult dog needs about 1.6 times RER, and an intact adult about 1.8 times. A puppy needs about 2 times RER, and a puppy under four months about 3 times. A senior needs less: about 1.2 to 1.4 times RER. The dog calorie calculator guide gives the same method with more worked examples, and the dog food portion calculator guide gives the portion sizes in cups and grams.
The dog food 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 dog, about 1.8 for an intact adult dog, about 2.0 to 3.0 for an active dog, about 2.0 for a puppy, and 3.0 for a puppy under four months, and about 1.2 to 1.4 for a senior. A lactating dog needs about 2 to 4 times RER, depending on the size of the litter.
| Body weight | Neutered adult (x1.6) | Intact adult (x1.8) | Active dog (x2.2) | Senior / weight loss (x1.3) |
|---|---|---|---|---|
| 5 kg | 375 | 420 | 515 | 305 |
| 10 kg | 630 | 710 | 865 | 510 |
| 15 kg | 855 | 960 | 1175 | 695 |
| 20 kg | 1060 | 1190 | 1455 | 860 |
| 25 kg | 1250 | 1410 | 1720 | 1015 |
| 30 kg | 1435 | 1615 | 1975 | 1165 |
| 40 kg | 1780 | 2005 | 2450 | 1445 |
Read the table from top to bottom and the pattern is clear: a dog's calorie needs rise with weight, but not in proportion — a dog 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 dog needs about 375 kcal a day as a neutered adult, a 10 kg dog needs about 630 kcal, and a 20 kg dog needs about 1060 kcal. The dog food calculator works out the exact figure for any weight and stage.
Worked examples
A 10 kg neutered adult dog: RER is 70 times 10 to the power 0.75, which is about 394 kcal, and daily calories are 394 times 1.6, which is about 630 kcal a day. A 25 kg neutered adult dog: RER is about 783 kcal, and daily calories are about 1,253 kcal a day. A 5 kg neutered adult dog: RER is about 234 kcal, and daily calories are about 375 kcal a day.
To work out your own dog's needs, weigh it, look up its RER in the table above, multiply by the factor for its stage, and divide the result by the calories in its food — which are printed on the bag or tin, usually as kcal per 100 g or per cup. A typical dry food has about 350 kcal per cup or per 100 g, but the only way to be sure is to check the bag. The how much food should a puppy eat guide gives the calorie tables for young dogs, and the senior dog diet guide covers feeding in the senior years.
How much food is that in cups and grams
A typical dry food has about 350 kcal per cup or per 100 g, so a dog that needs 630 kcal a day needs about 1.8 cups or 180 g a day, and a dog that needs 375 kcal a day needs about 1.1 cups or 107 g a day. Those are rough figures, because the calories in a food vary: a food with 400 kcal per cup needs less than a food with 300 kcal per cup, and a wet food has far fewer calories per gram than a dry food, because it is mostly water. Check the bag, and weigh the food — do not guess with a cup, because a cup of kibble can vary by a fifth depending on how full it is.
Split the daily amount into meals: a puppy needs three to four meals a day until about six months, then two meals a day, and an adult dog needs one to two meals a day. A young animal's stomach is small, so it cannot eat enough in one or two meals to meet its needs, and it needs food little and often. An adult dog can be fed once or twice a day, but twice is better: it keeps the stomach from being empty for too long, and it gives the dog something to look forward to. The how often should you feed a puppy guide gives the feeding schedule, and the how many calories should a dog eat per day guide gives the calorie tables by weight.
When the calculator is wrong
The calculator is wrong when the dog's weight is wrong, when the factor is wrong, or when the food's calories are wrong. Weigh your dog 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 dog 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 dog is ill, pregnant, nursing, or recovering from surgery: a pregnant dog needs more food in the last weeks, a nursing dog needs much more, and a sick dog may need a special diet. A dog that is losing weight on the calculated amount needs more food, and a dog that is gaining weight needs less — the scales and the body condition score matter more than the formula. The feeding a pregnant dog guide covers feeding in pregnancy, and the feeding a nursing dog 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 dog every month, feel its ribs and waist, and keep it at a body condition score of 4 or 5 out of 9. If your dog 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 dog that is at a healthy weight, eating a measured amount, and exercised every day, is a dog 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 dog — feeding guides on bags are often generous, because they are written for active dogs and because the maker wants you to buy more food. Trust the calculator, the scales, and your vet, not the bag. The dog food calculator works out the exact figure for any weight and stage, and the dog calorie calculator guide gives the same method with more worked examples.
For related reading, see the dog food calculator, the dog calorie calculator guide, the dog food portion calculator guide, the how much food should a puppy eat guide, the senior dog diet guide, the feeding a pregnant dog guide.
Frequently asked questions
How much food does a dog need?
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 1.6 for a neutered adult dog, 1.8 for an intact adult, 2.0 to 3.0 for an active dog, 2.0 for a puppy, and 1.2 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 dog 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 dog's life stage — about 1.6 for a neutered adult dog, or 1.2 for a neutered indoor cat.
How much should a 10 kg dog eat?
A 10 kg neutered adult dog needs about 630 kcal a day, which is about 1.8 cups or 180 g of a typical dry food with about 350 kcal per cup or per 100 g. Check the bag for the food's calories, and weigh the food.
How many meals a day should a dog have?
A puppy needs three to four meals a day until about six months, then two meals a day, and an adult dog needs one to two meals a day. A young animal's stomach is small, so it cannot eat enough in one or two meals to meet its needs.
Should I trust the feeding guide on the bag?
Not blindly — feeding guides on bags are often generous, because they are written for active dogs and because the maker wants you to buy more food. Trust the calculator, the scales, and your vet, not the bag. Weigh your dog every month, and adjust the food by a tenth at a time.
When should I ask a vet about feeding?
Ask your vet if your dog 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 dog, 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.