Feline obesity is one of the most consequential health problems in pet cats, and it is strongly associated with diabetes, arthritis and a shorter life. Most of it comes from free-feeding a bowl that is always full. This calculator uses the same formula veterinary nutritionists use — Resting Energy Requirement of 70 multiplied by weight in kilograms to the power of 0.75, then a life-stage multiplier — and converts the result into grams of your food.
A cat's daily calorie requirement is small, and the difference between the right amount and half again as much is a few grams of kibble. That is invisible in a bowl.
Neutering lowers energy requirements noticeably while appetite often stays the same, which is why the weeks after neutering are when many cats start gaining. A neutered adult cat sits around 1.2 times resting energy — lower than most owners expect.
Free-feeding makes the problem invisible because nobody is measuring. Measured meals, even two a day, give you a number you can adjust.
Wet food is roughly three-quarters water, so the calorie content per gram is far lower than kibble. A cat eating wet food eats a much larger physical volume for the same calories, which is part of why wet-fed cats often seem more satisfied.
If you feed both, calculate in calories rather than grams, and split the daily total between them. Manufacturers publish kcal per can or per 100 g; the calculator converts from whatever energy figure you have.
There is a second reason wet food matters. Cats have a weak thirst drive and do not fully compensate for a dry diet by drinking more, and low water intake is part of the picture in urinary and kidney disease. That is a conversation worth having with your vet, especially for a male cat or one with any urinary history.
This is the most important safety point on this page. A cat that loses weight too quickly — or stops eating altogether for a few days — can develop hepatic lipidosis, a serious liver condition. Overweight cats are at higher risk, which is exactly the population trying to lose weight.
Feline weight loss should be vet-supervised, gradual, and usually involves a diet formulated for it rather than simply less of the current food, so the cat still gets adequate protein and nutrients from a smaller portion.
Never starve a cat into eating something new, and never let a cat go without food for more than a day in the hope it will accept a change.
Feel along the ribs with flat hands. You should find them easily under a thin layer, without pressing. Look from above: there should be a visible waist behind the ribcage. Look from the side: the belly should tuck up rather than hang.
A pad of fat swinging under the belly is not always excess weight — many cats have a primordial pouch, which is normal anatomy. Judge by the ribs and waist instead.
Weigh the cat monthly on the same kitchen or baby scales. A cat gaining half a kilogram has gained a large fraction of its body weight, and you will not see it happening.
Start with 70 multiplied by weight in kilograms to the power of 0.75 for resting energy, then multiply by a life-stage factor — around 1.2 for a neutered adult, 2.5 for a kitten. That figure is a starting point; adjust monthly based on body condition and weight.
Free-feeding a kitten is usually fine. Free-feeding an adult cat is how most feline obesity starts, because nobody is measuring and the difference between the right portion and too much is a few grams. Measured meals give you a number you can actually adjust.
Calculate in calories rather than grams and split the daily total between them. Wet food is around three-quarters water, so the same calories come as a much larger physical portion — which is one reason wet-fed cats often seem more satisfied.
With your vet, and slowly. A cat losing weight too fast, or not eating for a few days, can develop hepatic lipidosis, a serious liver condition, and overweight cats are at higher risk. Vets usually use a diet formulated for weight loss rather than simply less of the current food.
Not necessarily. Many cats have a primordial pouch — a normal flap of skin and fat along the lower belly. Judge condition by feeling the ribs and looking for a waist from above, not by the pouch.