Dog Food Calculator

This calculator works out a dog's daily energy requirement the way a veterinary nutritionist does: it takes the resting energy requirement, 70 multiplied by body weight in kilograms raised to the power of 0.75, then multiplies that by an activity factor between 1.2 and 1.8 depending on how the dog actually lives. A neutered 20 kg dog with moderate activity therefore comes out near 1,000 calories a day. Those calories are then converted into portions using the energy density of each format: around 380 calories per cup of dry kibble, 250 per 13 oz can of wet food and 30 per ounce of raw. Two figures matter for using the result properly. Enter the dog's ideal weight rather than its current weight if it is overweight, and treat the answer as a starting point that the scales confirm or correct over the following fortnight, since individual needs vary by twenty to thirty per cent.

How It Works

Where the Formula Comes From

The resting energy requirement equation, 70 times body weight in kilograms to the power of 0.75, is the one used in veterinary practice and in the nutrition textbooks, and the exponent is the point of it. Energy needs do not rise in step with body weight: a dog twice as heavy needs roughly seventy per cent more energy, not twice as much, because the metabolically expensive organs make up a smaller share of a larger body. This is why scaling a large dog's ration down for a small dog underfeeds it, and why a chart organised by weight bands is always a compromise.

The activity factor that multiplies it carries the rest of the story. A neutered adult dog living a quiet indoor life sits near 1.2 to 1.4; a dog walked an hour or two a day, 1.5 to 1.6; a dog running or training hard, 1.6 to 1.8; and a working dog in cold weather can exceed 2. Growth, pregnancy and lactation use higher factors still, which is why a puppy or a nursing bitch is not calculated the same way as an adult. Neutering lowers requirements measurably, by something like ten to twenty per cent, and it is one of the commonest reasons a ration that used to be right stops being right.

Turning Calories Into a Portion You Can Measure

The calculator converts calories into cups, cans and ounces using average energy densities, and those averages are where the error creeps in. Real dry foods run from about 300 calories per cup for a weight-control formula to over 500 for a performance one, a spread of more than a third, so the cup figure here is an estimate until you check your own bag. The number to look for is the kcal per kilogram, which every complete food declares, and it turns an estimate into a measurement.

Do it once and the problem disappears. Divide the daily calories by the food's calories per kilogram to get the grams your dog needs, weigh that amount into your usual scoop, and mark the level. From then on the scoop is calibrated for that food, and the calculation is only repeated when the food changes. For a dog fed twice a day, halve the figure rather than eyeballing two similar scoops, and remember that treats come out of the daily total rather than being added to it.

Checking the Result Against the Dog

No formula knows your dog. Individual requirements vary by twenty to thirty per cent around the calculated figure, depending on metabolism, coat, housing, temperament and the particular food's digestibility. That is why the calculated ration is a starting point with a review date rather than an answer. Feed it for two weeks without changing anything else, then weigh the dog on the same scales and put both hands over the ribs: easy to feel under a thin layer of cover, a waist visible from above and a tuck behind the ribs from the side is what a correct ration produces.

If the dog has gained or lost more than about two per cent of its body weight, adjust the daily total by ten per cent in the appropriate direction and review a fortnight later. Repeat until the weight holds. A dog that keeps losing weight on a ration it should hold on, or that fails to lose weight on a genuinely restricted one, has told you something the calculator cannot: that is a reason for a consultation and a blood test rather than a further adjustment, since dental pain, thyroid disease and Cushing's syndrome all show up this way.

Breed-Specific Feeding Guides

For breed-specific recommendations including health-based adjustments and growth charts, check our detailed feeding guides:

Frequently Asked Questions