Cat Calorie Needs Calculator

Feeding a cat the right number of calories is one of the most important aspects of feline health care. Both overfeeding and underfeeding have serious consequences: obesity in cats is linked to diabetes, arthritis, and heart disease, while underfeeding causes muscle wasting and nutritional deficiencies.

The Feline Energy Requirement Formula

The World Small Animal Veterinary Association (WSAVA) and most veterinary nutrition guidelines use the following formula:

Resting Energy Requirement (RER) = 70 × (body weight in kg)^0.75

The RER is then multiplied by a life stage factor (also called the “illness factor” or “life factor”) to get the Daily Energy Requirement (DER):

DER = RER × Life Stage Factor

Life Stage Factors for Cats

Note what the weight-loss row multiplies. It is 0.8 × RER, the resting figure, not 0.8 × DER. Applying it to maintenance instead would leave a cat eating far too much to lose anything.

Weight loss in cats is not the same problem as in dogs

A cat that stops eating, or that is dropped onto a severe restriction, can develop hepatic lipidosis: the liver is flooded with fat mobilized faster than it can process, and it fails. It is the most common liver disease in domestic cats, it can start within a few days of a sharp drop in intake, and it kills cats that were merely overweight.

So two rules sit above the arithmetic:

• Aim for about 1% of body weight per week, and never sustain more than 2%. A 6 kg cat losing 1% a week takes roughly four months to reach 5 kg. That is the correct speed, not a disappointing one.
• A cat that refuses the new food is an emergency, not a stubborn cat. If it eats little or nothing for two days, stop the diet and call the vet.

Kittens, pregnant cats and nursing queens are never candidates for calorie restriction. A growing or lactating animal that is short of calories does not get slimmer, it gets developmental problems or stops producing milk.

Example Calculation

A neutered 4 kg (8.8 lb) adult indoor cat:

• RER = 70 × (4)^0.75 = 70 × 2.83 = 198 kcal/day
• DER = 198 × 1.2 = 238 kcal/day

How Much Food Is That?

Calorie density varies significantly between food types:

• Dry kibble: typically 300–450 kcal per 100g. This calculator assumes 370, and a level 8 oz measuring cup holds roughly 100 g of kibble.
• Wet canned food: typically 90–120 kcal per 100g. This calculator assumes 112, which puts a 5.5 oz (156 g) can at about 175 kcal.
• Raw or home-cooked: varies widely, check individual recipes

Important Note

These are starting points. Individual cats vary in metabolism. Monitor your cat’s body condition score (BCS) monthly and adjust food amounts by 10% if the BCS is trending outside the ideal range. Always consult your veterinarian for personalized feeding advice, especially for overweight, senior, or health-compromised cats.