How much should I feed my cat to lose weight?

Feed a cat for weight loss at its ideal weight, not its current weight. A cat whose ideal weight is 4 kg needs roughly 158 kcal a day — RER = 70 × 40.75 ≈ 198 kcal, multiplied by 0.80 — which is about 47 g of a 370 kcal/cup food, split across 2 meals. That is about 80% of its resting energy at the ideal weight — a 20% deficit from the RER baseline.

Gram figures assume a 370 kcal/cup food and the calculator's default of 110 g per cup — use your own bag's grams-per-cup figure for your food.

Why the ideal weight is the number that matters

Feeding for the current weight maintains the current weight; feeding for the ideal weight creates the deficit that gradual loss depends on. So a 6 kg cat with an ideal weight of 4.5 kg, fed at the 6 kg maintenance level, takes in about 25% more than the maintenance level for its ideal weight — and about twice the weight-loss target.

This is the single most common arithmetic error in cat weight loss, and it is not a rounding issue: it is the difference between a plan that works and one that quietly holds the weight steady.

Where these numbers come from

Every figure above is produced by the same calculation engine that runs the calculator on this site, in two steps:

1. Resting energy requirement: RER = 70 × kg0.75 — the NRC energy equation, taken at the cat's ideal weight.
2. Weight-loss factor: × 0.80 applied to that RER.

The 0.80 factor sits at the top of the range that veterinary guidelines use for feline weight loss. The plan page on this site describes the accepted band as 60–80% of the ideal-weight RER; we use the conservative end of it, because the faster end of that band is where the feline-specific risk below comes from. Cats must not lose weight quickly — the commonly cited ceiling is 1–2% of body weight per week, and exceeding it risks hepatic lipidosis.

The same factor tables, with their sources, are published in the open reference dataset (CC BY 4.0) — so any number on this page can be re-computed independently. Our full method is described on how we check our numbers.

Work out your own cat's number

The table covers common ideal weights. The calculator takes your cat's current weight and your vet's ideal-weight target, applies the factor above, and converts the result into grams or cups of your own food:

Open the cat calorie calculator →

How fast is safe

No more than 1–2% of body weight per week — for a 6 kg cat, roughly 60–120 g per week. Weigh on the same scale at the same time of day, and judge progress over a month rather than a week: plateaus are normal even when the plan is working.

One point is specific to cats and worth stating plainly: a cat that stops eating during a diet is a veterinary matter, not a discipline problem. Significant caloric restriction lasting 48–72 hours can cause hepatic lipidosis, which is frequently fatal, and overweight cats are at the highest risk. If your cat has eaten nothing for 24 hours, call your veterinarian.

Common follow-up questions

Can my cat lose weight on dry food alone? Yes, with precise measurement. Dry food's higher energy density means smaller volumes, which some cats find less satisfying. Wet food's moisture content raises satiety per calorie, so a mixed plan often makes a reduced target feel less like deprivation — see wet vs dry cat food for the trade-offs.

Should I use my cat's current weight or the ideal weight? The ideal weight, always. The calculator asks for both because the current weight sets the safe weekly loss rate, while the ideal weight sets the calorie target.

What if the weight stalls for two or three weeks? The target may need adjusting, but adjust gradually rather than cutting sharply. If your cat reaches its ideal weight, step back up to a maintenance level calculated at that ideal weight — otherwise the deficit becomes the new normal and the weight returns.

The full weight-loss plan, step by step →  ·  Score your cat's body condition →  ·  Cat calorie calculator →  ·  Open dataset →