Pet Food Portion Calculator (Dog & Cat)

Resting Energy Requirement (RER) is the number of calories an animal burns over 24 hours at complete rest in a thermoneutral environment — essentially the metabolic floor needed to keep the body running. Veterinary nutritionists use RER as the anchor because it scales smoothly with metabolic body size using the allometric formula 70 × (kg)^0.75. Every life-stage and activity factor (1.2× for a neutered adult cat, 1.8× for an intact adult dog, 4× for a working dog, and so on) is simply a multiplier on top of RER. This two-step approach is more accurate than feeding charts based on raw body weight because metabolic rate does not scale linearly with weight — a 40 kg dog does not need four times the calories of a 10 kg dog.

Cats are obligate carnivores with a more conservative energy budget than dogs. Their natural lifestyle of short hunts and long naps means a neutered adult cat typically needs only 1.0-1.2× RER, while a comparable adult dog needs 1.4-1.8×. Cats also have a far smaller difference between intact and neutered metabolic rates than dogs do. On the other end, working and sporting dogs can burn 3-8× RER during intense exercise, while no domestic cat has a multiplier higher than about 1.6×. These differences come from millions of years of divergent evolution and are reflected in the WSAVA Global Nutrition Committee feeding guides.

The same volume of food can deliver wildly different calories. Dry kibble is typically 300-450 kcal per 100 g because it is dehydrated, while canned wet food often runs 70-110 kcal per 100 g because it is 75-80% water. A cup of high-calorie performance kibble may have twice the calories of a cup of weight-management kibble. Feeding by the bag chart without checking the Metabolizable Energy (ME) label is a primary reason pets are overweight. Reputable brands print the kcal/kg or kcal/cup figure on the bag, on their website, or both — when in doubt, ask the manufacturer.

Body-condition score is a hands-on, visual assessment used by vets to grade body fat on a 1-9 (or 1-5) scale, where the middle of the scale is ideal. At an ideal score you should be able to feel ribs easily through a thin fat covering, see a tucked abdomen from the side, and see an hourglass waist from above. Above ideal, the waist disappears and the ribs become hard to feel. BCS is the gold-standard real-world check on any calorie calculation — if your pet's BCS drifts up while you feed the calculated amount, reduce the portion by 10-20% and reassess in 2-4 weeks.

Yes. Pregnant or lactating animals, growing large-breed puppies, pets with diabetes, chronic kidney disease, hyperthyroidism, pancreatitis, inflammatory bowel disease, cancer, or any animal on a prescription diet all have specialized energy and nutrient targets that cannot be captured by a generic RER calculator. The same goes for pets transitioning off a weight-loss program, dogs in heavy training cycles with day-to-day variable workloads, and very young or very old pets with unusual body composition. In all of these cases, ask your veterinarian or a board-certified veterinary nutritionist (DACVN) to set the calorie target.