How much should I feed my dog or cat?

Start with the resting energy requirement (RER), which is 70 multiplied by your pet's body weight in kilograms raised to the power of 0.75. A 20 kg (44 lb) dog has an RER of about 660 kcal. Multiply that by a life-stage and activity factor — roughly 1.6 for a typical neutered adult dog, 1.2 for a typical indoor adult cat, 3.0 for a puppy under four months — and you get the daily energy requirement this calculator uses. These figures come from the WSAVA Global Nutrition Committee feeding guidelines and AAHA weight-management guidance.

Divide the daily calorie target by the food's calorie density. Every label states kcal/kg (sometimes written as ME kcal/kg). If a food provides 3,700 kcal per kilogram — that is 3.7 kcal per gram — a 660 kcal daily target works out to about 178 grams. This method works for dry and wet food alike, which is why our table gives grams rather than cups: a can of pate and a scoop of kibble can differ by a factor of four in calorie density.

Because a cup is a measure of volume, not of energy. Kibble density ranges from roughly 90 to 130 grams per cup depending on the shape, size and air content of the pieces, so a cup of one food can carry 40% more calories than a cup of another. We give grams, which are exact for the stated kcal/kg, and show an approximate cup figure for dry food based on 110 grams per cup. Weigh one cup of your own kibble once and you will have an accurate conversion for that bag.

It gives a reasonable starting point, but growth is the one case where a calculator should not have the final word. Puppies and kittens need more energy per kilogram than adults and their requirement changes every few weeks, so weigh them weekly and adjust. Foods labelled for all life stages are formulated to support growth; foods labelled for maintenance only are not suitable for a puppy or kitten, and our results filter accordingly.

Individual requirements vary by roughly plus or minus 20% around any calculated figure, because age, neuter status, body condition, coat, ambient temperature and activity all move the number. Treat the result as a starting point: feed it for two weeks, then check body condition by feel — ribs easy to find under a thin layer but not visible, a waist behind the ribs from above. Adjust by 10% at a time rather than jumping to a new target.

Yes, with a caveat. The weight-loss option starts you at 80% of the maintenance requirement, which is the usual starting point for a controlled reduction. But obesity is a clinical condition, and rapid loss is dangerous — especially in cats, where losing weight too fast can trigger hepatic lipidosis. Ask your veterinarian to confirm the target weight and the rate of loss, then recheck every four weeks. If your pet is losing weight without you restricting food, that is a symptom to investigate, not a feeding problem.