How many grams of food a dog or cat needs per day, worked out from the veterinary energy equation and the caloric density on the food label.
A dog or a cat does not spend energy in proportion to its weight: a 40 kg dog does not need twice the food of a 20 kg one, but about 1.68 times as much. The relationship follows a power law first measured by Max Kleiber in the 1930s and refined for companion animals by the National Research Council. The resting energy requirement, RER, is 70 multiplied by the body weight in kilograms raised to the power of 0.75. That number is what the body burns lying still; a multiplier for the life phase — neutered adult, growing puppy, pregnant in the last third, working dog — turns it into the maintenance energy requirement, MER. The multipliers come from the WSAVA Global Nutrition Guidelines and the FEDIAF feeding tables, and they are published as ranges rather than single numbers precisely because breed, build, climate and temperament move the real need inside that range.
The number that actually decides how much food goes into the bowl is not the energy need but the caloric density of the food, printed on the label as metabolisable energy in kcal per kilogram. Divide by a thousand and you have kcal per gram. The same 900 kcal need turns into 214 grams of a high-energy kibble at 4.2 kcal/g and 310 grams of a light kibble at 2.9 kcal/g — almost a hundred grams of difference per day, which over a month is three kilograms of food. A calculator that uses a generic average instead of the real label is guessing the most important variable, and this page defaults to a generic average only so you have something to look at while you fetch the bag. The moment you type the real density, the result is arithmetic rather than a guess.
Treats are food. The WSAVA and the FEDIAF both recommend that no more than ten per cent of the daily energy comes from anything other than the complete food, including dental sticks, training treats and table scraps. Beyond that threshold the diet becomes unbalanced even if the calorie total is correct, because treats are not formulated to cover the micronutrient profile the complete food is designed to provide. This page shows the ten per cent in kcal so you can read the treat label and compare. The result runs entirely in your browser — the weight is never uploaded — and it is a starting point: the feeding plan of a puppy, a kitten, a pregnant animal, an overweight one or a sick one belongs to the vet, not to a web page.
RER = 70 × weight(kg)^0.75. MER = RER × life-phase factor (for example 1.6 for a neutered adult dog). Daily grams = MER ÷ caloric density of the food in kcal/g. Treats limit = MER × 0.10.
From the WSAVA Global Nutrition Guidelines, which consolidate the NRC (2006) and the FEDIAF feeding tables. They are published as ranges — for example 1.4 to 1.8 for a neutered adult dog — because breed, build and activity level move the need inside that range.
Because the caloric density of the food is the divisor in the equation. Two foods can differ by 40% — 2.9 kcal/g in a light kibble against 4.2 in a premium one — and the same energy need produces a very different portion. Without the label the calculator is guessing the number that matters most.
No more than ten per cent of the daily energy should come from treats, dental sticks or table scraps. The complete food is formulated to cover vitamins and minerals in proportion; treats are not, so exceeding ten per cent unbalances the diet even if the calories add up.
No. The calculation runs in JavaScript on your device. Nothing is uploaded, stored or logged.
Yes — there is a life phase for puppies and kittens, and the multiplier is higher. But the growth period changes fast, and the vet should be setting the plan and adjusting it at each visit.
Because the multiplier published by the WSAVA is a range. A neutered adult dog, for example, can need anywhere from 1.4 to 1.8 times the resting energy, depending on how active it is. The page shows the spread so you can see where the uncertainty lives.
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