Cat Feeding Calculator

How many calories a cat needs, in two steps

Feeding a cat comes down to calories, and calories come from weight. The first step finds the resting energy a cat burns doing nothing at all, and the second step multiplies that by a factor for life stage and activity. The answer is the number of calories to put in the bowl each day.

Resting energy = 70 x (body weight in kilograms to the 0.75 power)

Daily calories = resting energy x life stage factor x 0.85 if the cat is spayed or neutered

The exponent of 0.75 is there because energy use does not scale in a straight line with weight. A cat twice the size of another does not burn twice the calories, it burns about 1.7 times as many. This is the same allometric scaling used for dogs and for most mammals, and it is why a 20 lb cat does not need double the food of a 10 lb cat.

Once you have calories, portion size is a division problem. Divide the daily calories by the calories in a cup of your cat's dry food, or by the calories in a can of its wet food. The number on the bag or can is the only other thing you need.

Worked example: a 10 lb neutered adult

Take a 10 lb cat, four and a half kilograms. Raise 4.54 to the 0.75 power and you get 3.11. Multiply by 70 and the resting energy is 217 calories a day.

Now apply the life stage. An adult cat at maintenance uses a factor of 1.4, which gives 304 calories. Neutering lowers energy use by about 15 percent, so multiply by 0.85 and the daily target is 259 calories.

Divide that by a dry food at 400 calories per cup and you get 0.65 cups a day. Divide by a 3 oz can of pate at 80 calories and you get 3.24 cans. Split either amount across two meals and the bowl gets 0.32 cups or 1.6 cans at a time.

A mixed diet is a blend of the two. Feed 60 percent of the calories as dry food and 30 percent as wet, and the dry portion is 155 calories, which is 0.39 cups, while the wet portion is 78 calories, which is 0.97 cans. The remaining 10 percent is the treat budget, about 26 calories, or six or seven small treats.

Sanity check the number against the label. A 259 calorie day for a 10 lb cat is 26 calories per pound, which sits inside the 20 to 30 calories per pound range most veterinary sources give for an indoor adult. If your arithmetic lands far outside that band, something in the inputs is off.

Calories per day by weight and life stage

These rows are pre-computed so you can skip the formula. Every column except the intact adult column includes the 15 percent neuter adjustment, since most indoor cats in the United States are altered.

Read the table with the body condition in mind, not just the weight. A 12 lb cat with a visible waist is fine and a 12 lb cat shaped like a loaf is not, and the same calorie number applies to both. The table gives a starting point, and the scale over the next four weeks gives the answer.

Kittens are the big exception. A kitten at six months can eat nearly twice what its adult weight suggests, because it is still building bone and muscle. Feed kittens free choice or on a schedule with as much as they will eat in 20 minutes, and switch to the adult number once growth stops around 12 months.

Dry food and wet food are not close in calories

This is where most feeding mistakes happen. A cup of dry food and a can of wet food look like similar amounts of food and are nothing alike in calories. Dry kibble is roughly 400 calories per cup, and a 3 oz can of pate is about 80. Ounce for ounce, dry food carries three to five times the calories.

That gap explains a common story. A cat switched from dry to wet food without changing the volume eats far fewer calories and loses weight fast, sometimes faster than is safe. Go the other direction and the cat gains weight on what looks like a smaller bowl. The calories are what matter, not the volume.

Wet food has one clear advantage beyond calories: water. A 3 oz can is about 78 percent water, so a cat on wet food takes in much more moisture than a cat on kibble. Cats evolved as desert hunters and have a weak thirst drive, so the extra water supports kidney and urinary health. Many vets suggest at least half the diet as wet food for that reason alone.

Read the label for the calorie figure, usually printed as kcal per cup, kcal per can or kcal per kilogram. If the label only gives kilojoules, divide by 4.184 to get calories. If it only gives a percentage analysis, the guaranteed analysis on the bag, you cannot get calories from it directly and need the manufacturer's figure.

Cups and cans per day for a neutered adult

This table turns the calorie numbers into scoops and cans, using a 400 calorie cup of dry food and an 80 calorie 3 oz can. If your food is denser or lighter, the calorie column is the one to use and the portion columns will shift.

Two meals a day suits most adult cats. One large meal can cause a cat to eat fast and vomit, and free feeding dry food all day is the single most common cause of feline obesity. Measured meals also let you notice a drop in appetite within a day, which is often the first sign of illness in a cat.

Weigh the food rather than scooping it when you can. A kitchen scale reading in grams is more repeatable than a measuring cup, since kibble settles and a packed cup can hold 20 percent more than a loose one. A 400 calorie per cup food is about 100 calories per ounce, so a 26 calorie meal is 0.26 oz, or 7 grams.

The spay and neuter adjustment, and why 10 to 20 percent

Altered cats use less energy. Removing the reproductive organs lowers resting metabolism by roughly 10 to 20 percent, and it also lowers the hormones that drive roaming and searching for a mate. A neutered cat that keeps eating the same amount gains weight on a smaller frame of activity.

The calculator applies 0.85, which is a 15 percent cut, the middle of the range. A cat that was already lean and active before surgery might need only a 10 percent cut, and a cat that became sedentary after surgery might need 20 percent. Watch the ribs and the waist, adjust by 10 percent at a time, and give each change three to four weeks before judging it.

The effect is not small. On a 10 lb cat, 15 percent of 304 calories is 45 calories a day, which is about 0.11 cups of dry food. That is the difference between holding weight and gaining a pound over four months, since a pound of cat weight is roughly 3,500 calories of surplus.

Weight loss needs a different approach again. The 0.8 factor in the table is for a cat on a controlled reduction, and it should not go below 0.8 without a vet involved. Cats that lose weight too fast can develop hepatic lipidosis, a liver condition that is serious and expensive to treat. A safe rate is about 1 percent of body weight per week, so a 12 lb cat should lose no more than 2 oz a week.

Free feeding, treats and the scale as the real test

A calorie target is a hypothesis. The scale is the experiment. Feed the calculated amount for four weeks, weigh the cat on the same scale at the same time of day, and adjust by 10 percent if the weight moved the wrong way or moved too fast.

Treats are the hidden calories. The rule most vets use is that treats stay under 10 percent of daily calories, which is 26 calories for a 10 lb cat. A single soft treat is often 3 to 5 calories, a piece of cheese is 20, and a tablespoon of milk is 9. Three treats a day at 5 calories each is 15 calories, more than half of a 10 lb cat's 26 calorie treat budget, and enough to stall a diet.

Free feeding works for kittens and fails for adults. A bowl that refills itself removes the measurement, and most cats will eat past their needs when food is always available. If you need to leave food out for a cat that grazes, measure the day's portion into the bowl in the morning and do not add more until the next morning.

The FDA guidance on complete and balanced pet food explains what the label claim means and why a food that meets it can still be too calorie dense for an indoor cat. The Merck Veterinary Manual covers the energy requirements behind the formula, and the ASPCA cat nutrition guide has plain language advice on portions.

This is an estimate for planning, not veterinary advice. Kidney disease, thyroid disease, diabetes and pregnancy all change what a cat needs. Ask your vet before starting a weight loss plan or if your cat stops eating for more than a day.