Cats are quietly good at hiding how much they eat, because most of them are fed from a bowl that gets topped up rather than measured. Fill it when it looks low, add a few treats through the day, and the daily total is a mystery even to an attentive owner. That is part of why weight has become the most common nutrition problem vets see in cats. In its 2024 survey, the Association for Pet Obesity Prevention estimated that a majority of US cats, on the order of six in ten, sit in an overweight-to-obese body condition, a score of 6 to 9 on the standard scale, even while 55% of owners judged their own cat to be at an ideal weight (APOP). The gap is not neglect. It is arithmetic that never gets done, one refilled bowl at a time.
This guide replaces the topped-up bowl with two tools a vet uses: a calorie target and a body condition score. Calories give you a portion to start from. Body condition tells you whether that portion is actually right for your cat, which no chart can know. You will not need a spreadsheet or a drawer full of gadgets. You need a rough idea of how many calories your cat should eat, the one figure on the can or bag that turns that into a portion, and a monthly habit of putting your hands on the ribs. One thing comes before all of it: ask your veterinarian for your cat's ideal, or target, weight, because every number below is built on that figure, and a cat that is already lean should never be dieted (Cornell).
Start from a weight, not a full bowl
A bowl that is always full answers the wrong question. It tells your cat there is food, not how much food, and cats that free-feed all day rarely ration themselves down to what they actually need, especially indoor cats with little else to do. The trouble is scale. A cat is a small animal, so its daily calorie budget is small, often only a couple of hundred calories, and a few extra kibbles here plus a lick of gravy there add up to a real slice of that budget. On a large dog the same handful of stray calories disappears. On a nine-pound cat it does not.
There is a drift problem too, and neutering is the classic trigger. A portion that suited a young, intact, active cat is too much for that same cat a few months after it is spayed or neutered, when its energy needs fall. Nothing on the counter changes. The bowl looks the same, the cat looks the same for a while, and then the vet's scale reports a pound that took a year to arrive. Feeding to a weight rather than to a bowl does not stop your cat's life from changing. It makes the change show up as a number you can act on. So the first move is not to measure food at all. It is to get a target weight from your vet, the lean weight your cat should hold, and build every portion around that.
The nine-point check your hands can do
Before you count a calorie, learn to read your cat's body, because the scale alone cannot tell a big-boned cat from a fat one. Vets use a body condition score, a 9-point scale endorsed by groups such as the American Animal Hospital Association and the World Small Animal Veterinary Association, where 4 to 5 is ideal, 6 to 7 is overweight, and 8 to 9 is obese (AAHA, WSAVA). It is a hands-and-eyes read, not a weight, which is why it works the same on a slight Siamese and a heavy Maine Coon that share no common number on the scale.
Three checks do most of the work. Feel the ribs along the chest: at an ideal score you can feel them under a thin layer of fat, without pressing. Look down from above: there should be a slight waist behind the ribs, not an oval that bulges out on both sides. Feel the belly: an ideal cat carries only a small abdominal fat pad. One cat-specific caution here, because it trips up a lot of owners. The loose flap of skin that swings along a cat's lower belly, the primordial pouch, is normal anatomy and is not the same thing as a fat pad; plenty of lean cats have a noticeable one, so do not diet a cat over the pouch alone. Judge weight by the ribs and the waist, and if you are unsure, ask your vet to score your cat and guide your hands once. In APOP's 2024 survey only about four in ten cat owners were even familiar with body condition scoring, and fewer than three in ten recalled a vet giving their cat a score, so most people have simply never been shown (APOP).
The scale gives you a number. Your hands on the ribs tell you whether that number is a lean cat or a heavy one.
Turning a weight into daily calories
Here is the same math a vet uses, in plain terms. Every cat has a resting energy requirement, the calories it burns just staying alive, and the standard formula is RER = 70 × (ideal body weight in kg) raised to the power 0.75 (AAHA, WSAVA). From that resting figure you get the maintenance energy requirement, the calories for a normal day, by multiplying by a life-stage factor. For cats those factors run lower than most owners expect: roughly 1.2 for a typical neutered adult, about 1.4 for an intact adult, higher for a growing kitten or a genuinely active cat, and lower, set with a vet, for weight loss (WSAVA). The neutered-adult figure is worth sitting with, because it lands well below the equivalent number for dogs, and it is a large part of why cats gain after neutering when the bowl does not change.
Run it once with round numbers, used only to show the shape of the calculation, not as a target for your cat. Take a 4 kg cat, about 9 pounds. The resting requirement works out to roughly 200 calories a day, and multiplying by 1.2 for a neutered adult lands near 200 to 240 calories a day at maintenance, with many quiet indoor cats sitting at the low end or a little under. As of 2026, treat that as an illustration and get a real target from your vet, who will adjust for age, neuter status, activity and any health condition. You do not have to do the power-of-0.75 arithmetic yourself; most clinics, the AAHA and WSAVA guidelines, and the free calculators published by the Association for Pet Obesity Prevention will do it from an ideal weight. Understanding it just stops the portion from being a guess.
Reading calories off a can or a cup
A calorie target becomes a portion through one line on the package. Under AAFCO model regulations, US pet foods carry a calorie content statement under a heading reading "Calorie Content," given both as kilocalories per kilogram as fed and as kilocalories per a familiar unit, such as per cup for dry food or per can for wet (AAFCO). The per-unit figure is the one you actually feed by. For dry food, if your cat's target is around 240 calories a day and the bag reads 400 kcal per cup, then 240 divided by 400 is about 0.6 cup a day, split across meals. For wet food, if a 3-ounce can reads about 90 calories, that same target is roughly two and a half to three cans a day.
One figure will surprise you, and it is worth understanding before you compare foods. Canned food reads far lower in calories per kilogram than dry does, not because it is lighter or better, but because most of a can is water, so a lot of the weight carries no calories at all. That means you cannot line up a can's kcal-per-kilogram against a bag's and conclude anything; compare using the calorie statement per the unit you actually serve, and let the body condition score settle the rest. If you are weighing wet against dry for other reasons, our guide to wet versus dry cat food covers the tradeoffs, and either way the food should be complete and balanced for your cat's life stage, which is what the picks in the best cat food guide and, for the youngest cats, the best kitten food guide are chosen for.
Find your cat's daily calorie target from its ideal weight, then divide by the food's kcal per can or per cup to get the portion (AAFCO).
A cheap kitchen scale and grams per day is more honest than a scoop that packs differently each time, and on a small cat the error matters more.
Ribs easy to feel, a slight waist from above, a small belly pad. Aim for a 4 to 5 on the 9-point scale and recheck monthly (AAHA, WSAVA).
Split the daily ration into several small meals and puzzle or foraging feeders, which burn energy and slow a fast eater (AAFP).
Get the target weight from your vet and run any weight-loss plan past them, because losing weight too fast can trigger fatty liver disease (Cornell).
Free feeding, set meals, or a puzzle to hunt
How you deliver the ration matters almost as much as its size, and this is where cats part ways with dogs. A cat is a solitary hunter built to catch and eat many small prey across the day, not to graze from a trough, and the American Association of Feline Practitioners, in its consensus statement on how to feed a cat, notes that leaving a single bowl out ad libitum, or serving one or two big meals, ignores that biology and feeds boredom as much as hunger (AAFP). Its recommendation is to split the daily allowance into several small meals and, where you can, to serve some of it through puzzle or foraging feeders, food-dispensing toys and containers the cat has to bat, roll or paw at to release a few pieces at a time.
That does two things at once. It rations the food, so the day's calories are portioned instead of poured, and it turns eating into activity, which is exactly what a bored, under-exercised indoor cat is short on. A slow feeder or a treat ball can take a fast eater who inhales a bowl and brings it back up and stretch that same meal into ten minutes of work. You can buy puzzle feeders at every price, or make one for nothing from an egg carton or a plastic bottle with holes cut in it; start easy so the cat succeeds, then make them harder. Load the day's ration into the feeders in the morning so meals and treats both come out of the same daily number rather than on top of it, and keep treats to about 10%, and no more than 10 to 15%, of the day's calories (Cornell). Activity level is part of the calculation too, which is one more reason an indoor or outdoor lifestyle shifts how much a given cat needs.
When the number needs a vet, not a calculator
A calorie figure gets you a starting portion, never a finished one, because the formula assumes an average cat and yours is a specific one. So feed the calculated amount for a few weeks, then score the body again. If the waist is softening and the ribs are harder to find, trim the portion by a small amount, around 10%, and recheck. If the ribs are turning sharp and the belly is tucking up too far, add a little. Adjust in small steps and weigh on the same scale every couple of weeks, since a half-pound swing on a cat is a large fraction of its whole body.
Two situations belong with a veterinarian before you change anything, and the first is specific to cats. A cat should never be crash-dieted. Cutting a cat's intake sharply, or a cat that simply stops eating for a couple of days, can trigger hepatic lipidosis, a serious fatty liver disease that can take hold within a week or two of a major drop in food (VCA). Safe weight loss for a cat is slow, on the order of 0.5% to 2% of body weight a week, which means a real diet is measured in months and is set and monitored by your vet, often on a food formulated for it. The second is any cat whose needs sit outside the standard factors: a growing kitten, a pregnant or nursing queen, a senior, or a cat with a health condition. Cornell's own guidance draws a line worth repeating: a veterinarian should examine any cat that refuses to eat and is losing weight, rather than waiting to see whether it passes. If your cat's appetite or weight shifts without explanation, our guide to signs your cat is sick covers what to watch for, but the next step is the vet, not the calculator.
- Get the target weight first. Ask your vet for your cat's ideal weight before you calculate anything; the whole portion is built on it (Cornell).
- Do the calorie math from that weight. RER = 70 × (ideal kg) to the power 0.75, then about 1.2 for a neutered adult, and let a calculator handle the exponent (AAHA, WSAVA).
- Read the calorie statement. Divide the daily target by the food's kcal per can or per cup to get the portion, and never compare wet and dry by weight (AAFCO).
- Serve it as small meals and puzzles. Portion the day's ration across several feedings and foraging toys, with treats inside the 10% budget (AAFP, Cornell).
- Score the body, not the bowl. Recheck ribs, waist and belly monthly, adjust by about 10%, and take any real diet slowly and with your vet.
Feeding a cat well is less about the brand in the bowl and more about the number behind the portion. Start from an ideal weight your vet gives you, turn it into a calorie target with the RER and life-stage math, and divide that target by the kcal per can or per cup on the label to get a portion (AAHA, WSAVA, AAFCO). Serve it as several small meals and puzzle feeders so the calories are rationed and the cat has something to hunt, keep treats inside the daily total, and let a monthly hands-on body condition score, not the size of the bowl, decide whether you trim or add (AAFP). One line stays fixed through all of it: the math gives you a starting range and your veterinarian confirms it, most of all before any weight-loss plan, because a cat that drops weight too fast can get dangerously sick.
Portions and feeding, answered
It depends on your cat's ideal weight, life stage and activity, so the honest answer is a short calculation rather than a fixed number. Vets start from the resting energy requirement, RER = 70 × (ideal weight in kg) to the power 0.75, then multiply by a life-stage factor, about 1.2 for a typical neutered adult (AAHA, WSAVA). As an illustration only, a 4 kg (9 lb) neutered cat lands near 200 to 240 calories a day, and many quiet indoor cats need the low end or a little less. Treat that as a starting point and confirm a target with your vet, who will adjust for your specific cat.
For most indoor cats, portioned meals work better than a bowl left full all day. The American Association of Feline Practitioners recommends splitting the daily ration into several small meals and using puzzle or foraging feeders, because cats are built to hunt and eat many small prey, and a single ad libitum bowl tends to feed boredom as well as hunger (AAFP). Free feeding also hides how much your cat actually eats, which makes weight hard to manage. If you free-feed for a multi-cat household or scheduling reasons, at least measure the day's total and split it, rather than topping the bowl up by eye.
Look for a section headed "Calorie Content," usually near the guaranteed analysis on the label. By AAFCO model regulations it is given as kilocalories per kilogram as fed and as kilocalories per a familiar unit, such as per cup or per can (AAFCO). Feed by the per-unit figure: divide your cat's daily calorie target by the kcal per cup or per can to get the portion. A can reads far lower per kilogram than dry food because most of it is water, so do not compare a can's kcal per kilogram against a bag's; that difference is moisture, not richness.
Slowly, and with your vet. Safe weight loss for a cat is roughly 0.5% to 2% of body weight per week, so a genuine diet is measured in months, not weeks (Cornell). Cutting food sharply is dangerous: a cat that loses weight too fast, or stops eating, can develop hepatic lipidosis, a serious fatty liver disease that can set in within a week or two (VCA). That is why you should never put a cat on a weight-loss diet on your own. Ask your vet to set a target weight and a calorie plan, often on a food formulated for weight loss, and to recheck the progress.