Why per pound feeding rules fail small and large dogs

Published 2 October 2026. Not yet reviewed by a board certified veterinary nutritionist. Numbers marked as engine output come from the Petcare engine on the date shown.

Energy need per kilogram falls as dogs get bigger. At 1.6 x RER for a neutered adult, a 2 kg dog needs 94 kcal per kg a day, a 10 kg dog 63 kcal per kg and a 40 kg dog 45 kcal per kg. Fixed amounts per pound or percent of body weight miss one end.

The formula, and why the exponent matters

Resting energy requirement is 70 x body weight in kg^0.75 kcal a day. The exponent is the whole story. Energy use scales with metabolic body size, not with mass, so a dog twice as heavy burns 1.68 times as much, because 2^0.75 is 1.68. The equation and its life stage factors are the basis of the AAHA 2021 guidelines and the WSAVA Global Nutrition Toolkit calorie chart, and the feeding tables in the NRC owner booklet scale by the same kg^0.75 Grade A. The Merck Veterinary Manual also lists a linear shortcut, 30 x kg + 70, but marks it as valid only between 2 and 45 kg Grade C. Even that shortcut has a constant term of 70, which is the admission that a straight line through the origin, which is what every per pound rule is, cannot fit dogs.

Three dogs, computed

The table applies RER and the neutered adult factor of 1.6, the factor Petcare uses for a dog on daily walks. Per kg and per lb figures are the daily total divided by the dog's weight.

The 40 kg dog weighs 20 times the 2 kg dog and needs 9.5 times the energy. No single number per pound can describe both. A rule tuned to the 10 kg dog, where 28.6 kcal per lb happens to fit, gives the 2 kg dog 67 percent of its need and the 40 kg dog 142 percent. The 1.6 factor itself sits inside the consensus range: it equals 112 kcal per kg^0.75, and FEDIAF 2025 gives 110 kcal per kg^0.75 for dogs aged 3 to 7 years Grade A.

The "25 to 30 calories per pound" rule

Several brand and feed store pages say an adult dog needs 25 to 30 kcal per lb of body weight. Set against the formula, the rule gives the 2 kg dog 110 to 132 kcal, which is 30 to 41 percent short of 188 kcal. It gives the 10 kg dog 551 to 661 kcal, which brackets the formula's 630 kcal. It gives the 40 kg dog 2,205 to 2,646 kcal, which is 24 to 49 percent above 1,781 kcal. The rule is a tangent to the curve near 10 kg and nothing else. A toy breed fed by it loses condition; a large breed fed by it gains. Neither owner has done anything careless, they have used a number that was never true for their dog. Energy is not the only cost. A dog fed 40 percent above its need also receives 40 percent more of every mineral and vitamin in the food, and a dog fed 40 percent below receives too little of each, so a per pound error ripples through the whole nutrient supply.

The "2 to 3 percent of body weight" rule

Raw feeding guides usually scale food by weight instead of energy: feed 2 to 3 percent of the dog's body weight a day. This is the same straight line in grams instead of kcal. It gives the 2 kg dog 40 to 60 g, the 10 kg dog 200 to 300 g and the 40 kg dog 800 to 1,200 g, and the 40 kg dog again receives 20 times the food of the 2 kg dog for 9.5 times the need. The gram figure also hides the energy density of the food. Lean muscle meat, fatty mince, bone and offal differ in kcal per g, so 2 percent of a lean mix and 2 percent of a fatty mix are different diets. Petcare's own low budget recipe, at about 1.5 kcal per g, makes the point from the other direction: the engine's portion is 6.5 percent of body weight for the 2 kg dog, 4.3 percent for the 10 kg dog and 3.1 percent for the 40 kg dog. A percent rule can only be right for one size of dog eating one recipe.

The weights where each rule happens to work

Every flat rule is a tangent to the curve, so each one is correct for a narrow band of dogs. Solving 1.6 x 70 x kg^0.75 per pound of body weight shows where. The formula gives 30 kcal per lb at 8.2 kg (18 lb) and 25 kcal per lb at 17.1 kg (38 lb), so "25 to 30 kcal per lb" describes neutered adults of roughly 8 to 17 kg and nobody else. Below 8 kg the rule underfeeds, and the error grows as the dog shrinks: 42.7 kcal per lb is the true figure at 2 kg. Above 17 kg it overfeeds, reaching 20.2 kcal per lb at 40 kg. The percent rule has its own band. With a recipe of 1.5 kcal per g, the formula portion equals 3 percent of body weight at 38 kg and would not reach 2 percent until an impossible 194 kg. For that recipe, "2 to 3 percent" fits only dogs of about 38 kg and up. A denser food shifts the band down, which is the point: the band depends on the food, and the rule never says so.

Why a factor is still only a starting point

The formula gets the shape of the curve right; it does not get every dog right. In 586 client owned dogs the mean intake was 98 kcal per kg^0.75, with a coefficient of variation near 30 percent, and breed means ranged from about 82 to 113 kcal per kg^0.75 (Thes et al. 2016) Grade C. A meta analysis of 70 groups found 143 kcal per kg^0.75 on average with a standard deviation of 55, with working dogs highest and pet dogs lowest (Bermingham et al. 2014) Grade B. Measured resting energy fell within 20 percent of the RER prediction in only about half of 77 dogs (O'Toole et al. 2004) Grade B. FEDIAF notes that published allowances run from under 90 to about 200 kcal per kg^0.75 and that recommendations may overestimate need by 10 to 60 percent Grade A. So the curve replaces the flat rule, and the scale replaces the curve.

What to use instead

Use the three step method every guideline above describes. First, compute RER as 70 x kg^0.75 and multiply by the factor that fits the dog: 1.6 for a neutered adult on daily walks, 1.8 if intact, 1.4 if lazy or aged 7 and over, 2.0 if active (Grade A for the method, Grade C for the exact factors). Second, convert kcal to grams of the specific food by its energy density, which for a homemade recipe means summing the kcal of each ingredient. The APOP calculator does this conversion for commercial foods and states its formula Grade C. Third, weigh the dog every two to four weeks, score body condition on the WSAVA 9 point chart and adjust the grams by about 10 percent at a time Grade C. Puppies, pregnant or nursing dogs, dogs with a diagnosed condition and dogs that need to lose weight need a vet's plan, because their factors are different and the margin for error is smaller.

Check it with Petcare

The Petcare calculator computes RER, the daily kcal and the grams of a balanced recipe for your dog's actual weight, so you never have to borrow a per pound number.

Petcare is software, not veterinary advice. It builds recipes for healthy adult dogs. For puppies, pregnant or nursing dogs, dogs with a condition or food allergy a vet has diagnosed, dogs on medication, and dogs that need to lose weight, the diet should come from your vet.