Updated 11 October 2026 · Published by Radif Partners

Cat food calculator: how much should my cat eat?

Daily calories by the veterinary formula for kittens and adults, converted into cans of wet food or cups of kibble.

Merck Veterinary Manual energy factors · checked October 11, 2026

A spayed or neutered 10 lb cat needs roughly 261 kcal a day: a resting requirement of 218 kcal times 1.2. Cats need far less than most owners expect, and the gap between a neutered indoor cat and an intact one is large: the Merck Veterinary Manual uses 1.2 times the resting requirement for the first, 1.4 for the second, 1.0 for a cat that gains weight easily, and 2.5 for a growing kitten. This calculator applies those factors to your cat's weight and divides the result by the calories in a can of its food, or in a cup if you feed kibble; switch the field to whichever label you have. Because surplus calories in cats turn into fat quickly, and obesity drives diabetes and arthritis, the point of the figure is to give you a measured starting ration instead of a full bowl. Weigh your cat monthly and move the portion by a small step if the weight drifts.

Runs in your browser: nothing you type is sent or stored. A ration to start from and adjust by weigh-ins. How the figures are built.

From resting energy to a daily ration

The resting energy requirement is the same formula for cats as for dogs: body weight in kilograms raised to the power 0.75, times 70. A 4 kg (8.8 lb) cat has a resting need of about 198 kcal. Multiplied by 1.2 for a neutered adult, that gives about 238 kcal a day.

The factors are lower than for dogs. Many cats live indoors, sleep much of the day and, once neutered, need markedly fewer calories than before surgery while their appetite often increases. That combination is the usual route to an overweight cat.

Wet food, dry food or both

A typical small can of wet food holds far fewer calories than a cup of kibble, because most of its weight is water. Read the kcal per can on the label and enter it; for dry food, enter the kcal per cup and read the result as cups. The example value in the form only shows how the result looks.

If you mix both, decide how much of the day comes from wet food, subtract its calories, and give the remainder as kibble. Wet food adds water to the diet, which many cats, descended from desert animals, drink little of on their own.

Feeding a kitten

Kittens use about 2.5 times their resting requirement while they grow. Feed a food made for growth, enter the kitten's weight on the day, and recalculate every two weeks: its weight changes quickly.

Young kittens do best with several small meals a day. Neutering, often done before five months, lowers the energy need once growth slows, so expect to cut the portion during the first year rather than keep it rising.

Spotting overfeeding early

Run a hand along your cat's side: the ribs should be easy to feel under a thin layer, and from above there should be a visible waist. A belly pouch that swings when the cat walks is normal in many cats and not a sign of fat on its own.

A cat that loses weight without a diet change needs a vet visit rather than more food: kidney disease, hyperthyroidism and diabetes all cause weight loss, often in cats over ten.

Starting calories a day for an adult cat

Body weight	Resting need (RER)	Neutered × 1.2	Intact × 1.4
5 lb	129	155	181
6 lb	148	178	208
7 lb	167	200	233
8 lb	184	221	258
9 lb	201	241	281
10 lb	218	261	305
11 lb	234	280	327
12 lb	249	299	349
14 lb	280	336	392
16 lb	310	371	433
18 lb	338	406	473
20 lb	366	439	512

Computed with the Merck formulas; real needs can vary by 30% either way.

Not a substitute for a veterinarian

A cat that stops eating for more than a day or two can develop serious liver problems, and cats with kidney disease, diabetes or urinary problems need a diet set by a vet. Ask before cutting an overweight cat's food.

Sources

Merck Veterinary Manual, energy formulas and feline life-stage factors (read October 11, 2026)
WSAVA Global Nutrition Committee, nutrition assessment and body condition scoring (read October 11, 2026)
AAFCO, calorie statements on pet food labels (read October 11, 2026)

By Radif Partners Updated 11 October 2026

Frequently Asked Questions

A neutered 10 lb indoor cat needs about 261 kcal a day by the Merck formula, and a lazy or weight-prone one nearer 218. That is often less than one generous cup of kibble. Weigh the cat each month and adjust by small amounts, since a few extra kcal a day add up to pounds over a year.

Divide the daily calories by the kcal per can on the label. A 10 lb neutered cat at about 261 kcal eating a food with 80 kcal per 3 oz can needs roughly 3.3 cans a day. Larger 5.5 oz cans often carry nearly twice that, so always check the label rather than counting cans.

Neutering lowers the energy a cat burns while appetite tends to rise. Merck sets the factor at 1.2 times the resting requirement for neutered adults against 1.4 for intact ones, about 14 percent less. Keeping the old portion after surgery is one of the commonest causes of feline weight gain.

About 2.5 times its resting energy requirement while it grows, split over several meals. Enter the kitten's weight on the day and recalculate every couple of weeks. Kitten food is denser in energy and nutrients than adult food, so use the calories on its own label.