NNPets
This calculator could not start. It needs JavaScript to do its arithmetic, and that either failed to load or is switched off. The explanations, reference tables and cited sources below all work without it — and the formulas are written out under each calculator, so you can work through them yourself.

How many calories should an overweight pet eat?

The daily target from the AAHA 2021 weight-reduction figures, calculated from your pet’s ideal weight rather than its current one — which is the difference between a plan that works and one that quietly maintains the problem.

Do this with a veterinarian, not instead of one. This page asks you to enter the ideal weight your vet has set. It does not estimate one, and it does not predict how fast your pet should lose weight. If your pet is a cat, read the warning below before anything else.

Your pet

Not an estimate. If you do not know it, this is the number to ask your vet for.

kcal/kg

Weight-loss diets are usually less energy dense than maintenance food, so check the bag.

Results update as you type.

Daily calorie target

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kcal per day

Published range
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Per meal
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Grams per day
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What has to change

Currently eating to maintain
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Daily reduction
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Weight to lose
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Over ideal by
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Why the ideal weight, not the current one

This is the single most common mistake in home weight-loss plans, and AAHA address it in one sentence: “Base these calculations on ideal weight.” Feeding an overweight animal the calories it needs to maintain its overweight body keeps it overweight. The target has to be the weight you are trying to reach.

That is also why this page asks you to type the ideal weight rather than estimating it from a photograph or a body condition score. A wrong target weight produces a wrong calorie figure, and that figure then gets applied every day for months before anyone notices.

Cats are not small dogs, and this is where it matters most

Cats that stop eating, or lose weight too quickly, are at risk of hepatic lipidosis (fatty liver), which can be fatal. Feline weight-loss factors are deliberately conservative for this reason. Do not start a calorie-restricted diet for a cat without veterinary supervision, and contact a veterinarian urgently if a cat refuses food for more than 24 hours.

This is why the tool shows the warning whenever you select a cat, and why it does not tell you how fast your cat should lose weight. Rate is a veterinary decision made against weekly weigh-ins.

Two published formulas, slightly different answers

AAHA report the mean energy intake that produced weight loss over twelve weeks in each species: 63 ± 10.2 kcal/kg0.75 for dogs and 52 ± 4.9 kcal/kg0.711 for cats. Note that the exponents differ — the feline formula is not the canine one with a different multiplier.

An older route still appears in life-stage tables: multiply the resting energy requirement by 1.0 for a dog or 0.8 for a cat. This page shows both, because they disagree by roughly 10–17% depending on species and weight. A tool that showed you one and not the other would be hiding a real discrepancy between two published sources.

Why there is no weekly loss rate here. Converting a daily calorie deficit into kilograms of body fat needs a constant, and the usual one (about 7,700 kcal per kg) comes from human medicine rather than veterinary practice. Applied to cats it can produce rates above 2% of body weight per week, which is in the range that causes hepatic lipidosis. This site’s rule is that every number is traceable to a source; an untraceable number that can encourage a lethal rate does not belong on the page, so the rate is left to the veterinarian who can weigh the animal.

Frequently asked questions

Why does the calculation use my pet’s ideal weight instead of the current one?

Because feeding for the current weight maintains the current weight. AAHA state it directly: base these calculations on ideal weight. If you calculate from what the animal weighs now, you are calculating how to keep it that size.

How do I know my pet’s ideal weight?

Your veterinarian sets it, usually from a body condition score plus breed and frame. This page asks you to enter it rather than guessing it, because a wrong target weight silently produces a wrong calorie target, and that error is then applied every day.

Why is there no weekly weight-loss rate on this page?

Because producing one needs a conversion from calorie deficit to body fat, and the standard constant for that comes from human medicine. It can also output rates above 2% of body weight per week for cats, where losing weight quickly risks fatal liver disease. Your veterinarian sets the rate and monitors it by weighing.

Is this veterinary advice?

No, and this is the tool where that matters most. Weight reduction is a medical intervention with real risks, especially in cats. Use this to understand the target your vet sets, not to set one yourself.

Sources

  1. AAHA, 2021 AAHA Nutrition and Weight Management Guidelines — Weight Reduction in the Obese Pet. Source of the weight-reduction energy figures for both species and of the instruction to calculate from ideal weight. aaha.org
  2. AAHA and the Pet Nutrition Alliance, life-stage factors, for the older 1.0× and 0.8× routes shown for comparison. petnutritionalliance.org

For a pet at a healthy weight, the dog calorie calculator and the cat feeding calculator cover maintenance. How these sources were chosen, and what this site does not do: about & methodology.

Educational use only, and this one especially. Weight reduction is a medical intervention. Do not start, change or extend a weight-loss plan for any animal without veterinary supervision, and treat any rapid or unexplained weight loss as an emergency.