Pet Food Calculator

Pet daily food portion calculation determines the correct amount of food to feed your dog or cat each day based on weight, life stage, and the caloric density of the specific food you’re using.

Core formula: Daily Food Amount = Daily Calorie Need ÷ Food Calories per Cup (or per kg)

Step 1: Calculate Resting Energy Requirement (RER): RER (kcal/day) = 70 × Body Weight (kg)^0.75

Simplified linear approximation for most pets: RER ≈ 30 × Weight (kg) + 70

Step 2: Apply the life stage factor: Daily Energy Requirement (DER) = RER × Life Stage Factor

The factors are not the same for the two species, which is the part most feeding charts skip. A cat is a smaller animal running a slower engine, so its maintenance factor sits well below a dog’s. Feed a neutered indoor cat on the dog’s 1.6 and you are handing it a third more food than it needs, every day, forever.

Pregnancy and nursing sit outside this range entirely (a nursing dog can need 4 to 8 times its RER), so those are a conversation with your vet rather than a number off a chart.

Step 3: Divide by food caloric density: Most dry kibble: 300–400 kcal/cup. The figure has to be on the label, stated as kcal per cup or per kilogram, under AAFCO (Association of American Feed Control Officials) labelling rules. Most wet food: 100–200 kcal/can. Wet food varies far more than kibble, so read the can rather than guessing.

Worked example: A 10 kg (22 lb) neutered adult Labrador: RER = 70 × (10)^0.75 = 70 × 5.62 = 394 kcal/day DER = 394 × 1.6 = 630 kcal/day Kibble density: 350 kcal/cup Daily portion = 630 ÷ 350 = 1.8 cups per day (split into 2 meals)

The same 10 kg on the cat scale would be a very large cat indeed, but the arithmetic shows the gap plainly: 394 × 1.2 = 472 kcal, about a quarter less food for the same body weight.

Important: These are starting points, not prescriptions. Adjust against body condition score (BCS), a 1-to-9 scale your vet will use. A BCS of 5/9 is ideal, and the test is tactile: you should feel the ribs easily under a thin layer, without seeing them. Reduce by 10–20% if your pet is gaining, increase if losing, and reweigh every two weeks rather than eyeballing it. Fresh water always available.