Feeding guidelines on a bag are population averages, and most of them are generous. This calculator works from the two formulas veterinary nutritionists actually use: Resting Energy Requirement, which is 70 multiplied by your dog's weight in kilograms to the power of 0.75, and then a life-stage multiplier to reach the Maintenance Energy Requirement. Enter your food's calorie content and it converts that into grams a day.
Resting Energy Requirement is the energy a dog needs at complete rest. The formula, RER = 70 x (body weight in kg) ^ 0.75, is the standard allometric equation used across veterinary nutrition. It is not linear: a 40 kg dog does not need twice the calories of a 20 kg dog, it needs about 1.7 times as many.
Maintenance Energy Requirement multiplies RER by a factor for the dog's situation. A neutered adult sits around 1.6, an intact adult around 1.8, a puppy under four months around 3.0, and a genuinely working dog around 2.5. Those multipliers are published starting points, not measurements of your dog.
To turn calories into grams, the calculator needs your food's metabolisable energy in kcal per kilogram. Most manufacturers publish it on the bag or on their website, usually as kcal/kg or kcal per cup. If yours only gives kcal per cup, weigh one cup of the food and use that to convert — cups vary enormously between foods because kibble density does.
Any calculator gives you a starting point. The thing that tells you whether it is right is your dog.
You should be able to feel the ribs easily with flat hands and light pressure, without them being visible on a short-coated dog. From above, there should be a waist behind the ribs. From the side, the belly should tuck up rather than running straight back.
If you cannot feel ribs without pressing, reduce the portion by about ten per cent and reassess in a month. If ribs and spine are prominent and the dog looks angular, increase it. Weigh the dog monthly on the same scales — in a small dog a few hundred grams matters and you will not see it by eye.
A cup is a volume, and kibble density varies by more than a third between foods. The same scoop of a dense fish-based kibble and an airy grain-free one can differ by a substantial number of calories, which is how dogs gain weight on an unchanged routine after a food switch.
A cheap digital kitchen scale removes the problem entirely and is the single most effective weight-control tool most owners can buy.
Count treats. Treats, chews, training rewards and what goes in a stuffed toy should stay under about ten per cent of the daily calories, and they should come out of the day's total rather than being added on top.
Weight loss should be vet-supervised. Crash dieting is not safe, and a dog that needs to lose weight often needs the food changed rather than just reduced, so it still gets the nutrients it needs from a smaller volume.
Any diagnosed condition — kidney, liver, heart or pancreatic disease, diabetes — changes the calculation completely, and those dogs need a therapeutic diet prescribed for them.
Large-breed puppies are a special case. Overfeeding a large-breed puppy, and getting the calcium balance wrong, is associated with developmental joint problems. Use a food formulated for growth of large-size dogs and follow your vet's guidance on growth rate.
Start from the calculation: 70 x (weight in kg to the power 0.75) gives resting energy, then multiply by a life-stage factor — roughly 1.6 for a neutered adult. Convert to grams using your food's kcal per kilogram. Then adjust monthly based on body condition, because that figure is a population average rather than a measurement of your dog.
Bag guidelines are broad averages across a weight band and tend to be generous, partly because underfeeding generates complaints and overfeeding does not. They also cannot know whether your dog is neutered, working or elderly. Use them as a sanity check rather than an instruction.
Weigh it. Kibble density varies by more than a third between foods, so the same cup can hold noticeably different calories. Weighing is the single most effective weight-control habit most owners can adopt, and a kitchen scale costs very little.
You should feel the ribs easily with flat hands and light pressure, see a waist behind the ribs from above, and see the belly tuck up from the side. If you have to press to find ribs, the dog is carrying extra weight. Weigh monthly on the same scales, because gradual gain is invisible day to day.
Yes, and they are where most extra weight comes from. Keep treats, chews, training rewards and stuffed-toy fillings under about ten per cent of the daily calories, and subtract them from the day's total rather than adding them on top.