Cat Food Calculator

Cat food portions are calculated using veterinary formulas based on your cat’s weight, life stage, and activity level. This calculator determines daily calorie needs and converts them into cups of dry food or cans of wet food.

Step 1, the Resting Energy Requirement (RER):

RER = 70 × (body weight in kg)^0.75

This represents the calories needed just to maintain basic body functions at rest.

Step 2, the Daily Energy Requirement (DER):

DER = RER × Life Stage Factor

These are the same factors the cat calorie calculator uses, so the two pages cannot hand out different answers for the same cat. Kittens are split at four months on purpose: a very young kitten needs three times its resting requirement, and lumping the whole first year into one 2.5 band underfeeds a twelve-week-old by about a fifth at exactly the age when growth is fastest.

The 0.8 weight-loss figure is the standard veterinary starting point: 80% of the resting requirement, not 80% of maintenance. It is deliberately conservative. Cats that lose weight too fast can develop hepatic lipidosis, which is life-threatening, so a supervised loss of 0.5–1% of body weight per week is the target.

What each variable means:

• Body Weight: your cat’s current weight in pounds or kilograms. The calculator converts to kg internally since the formula uses metric units.
• Life Stage: determines the activity multiplier. Kittens need the most energy per pound because they are growing rapidly. Senior and overweight cats need fewer calories.
• Food Type: dry food, wet food, or a mix of both. Each has different calorie density.

Typical calorie content of cat food:

• Dry food: ~370 kcal per cup. A level 8 oz measuring cup holds roughly 100 g of kibble, so that is also about 370 kcal per 100 g.
• Wet food: ~112 kcal per 100 g, which works out to ~175 kcal in a 5.5 oz (156 g) can.

Practical example: A 10 lb neutered adult cat. Ten pounds is 4.54 kg, and 4.54^0.75 = 3.11, so RER = 70 × 3.11 = 218 kcal. DER = 218 × 1.2 = 261 kcal/day. In dry food that is 261 / 370 = about 0.7 cups per day. In wet food, 261 / 175 = about 1.5 cans per day.

Tips: Always split the daily amount into 2–3 meals rather than leaving food out all day, because free-feeding often leads to overeating. These calorie values are averages, so check your specific food’s label for its exact kcal per cup or can. If your cat is gaining or losing weight unexpectedly, consult your veterinarian to adjust portions. Fresh water should always be available, especially for cats on dry food diets.