Indoor cats live a very different life from outdoor cats, and their food bowl should reflect that. A cat that spends the day on a sofa, a windowsill, and a bed burns far less energy than a cat that roams gardens and climbs fences. Yet many feeding guides on packets give one amount for all cats, which is often too much for a quiet indoor life. This calculator adjusts the daily portion for indoor living, using the cat weight and how much it plays, and converts the result into grams you can weigh out.
The calculation starts with resting energy requirement, the standard formula of 70 times weight in kilograms to the power of 0.75. A 4 kilogram cat has a resting need of about 198 calories. For an indoor cat, the calculator multiplies that by a low activity factor: 1.0 for a cat that mostly sleeps, 1.1 for some daily play, and 1.2 for an active indoor cat. That gives a daily range of roughly 198 to 238 calories for a 4 kilogram cat, before treats. The food energy you enter then turns calories into grams.
Indoor weight creep is slow, which is why it is so easy to miss. A surplus of just 20 calories a day adds up to about 2 grams of body fat per day, which is more than 700 grams over a year. The cat does not look different from week to week, but the collar gets tighter and the waistline disappears. Regular weighing is the only reliable way to catch it early. Weigh your cat once a month at least, and weekly if you are adjusting the portion.
Here is a worked example. A 4.5 kilogram indoor cat that plays a little each day has a resting need of about 218 calories, times 1.1, which is about 240 calories per day. With food at 350 calories per 100 grams, that is about 69 grams per day. Split into two meals, that is roughly 34 grams per meal. If the same cat mostly sleeps, the amount drops to about 218 calories, or 62 grams. The difference is small on paper but large over months.
Packet guides are a starting point, not a rule. They are written for an average cat and they often lean generous, because a hungry cat complains loudly while an overfed cat stays quiet. Use the packet as a cross-check, then trust the scale and the weighing results. If the weight is steady over four weeks, the portion is right. If it climbs, cut by 5 to 10 percent and weigh again in two weeks. Never cut by a third in one go.
The type of food matters too. Wet food is mostly water, so a cat can eat a larger, more satisfying portion for the same calories. Many indoor cats do well on a mix, for example half the calories from wet food and half from dry. Wet food also adds water to the diet, which helps the urinary tract. Dry food is convenient and cheaper per calorie, but it is easy to over-pour, so always weigh it rather than guessing from a cup.
Boredom is the hidden driver of indoor overeating. A cat with nothing to do will visit the bowl out of habit, not hunger. Puzzle feeders, food hidden in boxes, and short play sessions before meals all help. Feed in two or three small meals at set times instead of leaving food down all day. A routine also lets you notice quickly if the cat stops eating, which can be an early warning sign of illness.
Treats need a budget. The common guidance is that treats should stay near 10 percent of daily calories. For a 240 calorie cat, that is only 24 calories, which is about two small commercial treats or a few pieces of kibble taken from the daily portion. Using kibble from the measured ration as treats is the simplest trick, because it adds nothing extra. Family members should know the rule, or the cat will learn to tour the house collecting extras.
Kittens, seniors, and cats with health conditions do not fit this calculator. Kittens need far more energy per kilogram because they are growing. Senior cats vary: some need fewer calories, while others with kidney or thyroid problems need more. Pregnant and nursing cats need much more food. This tool is for healthy adult indoor cats only, and any cat with a medical condition should be fed to a vet plan.
Season and home temperature also play a small part. Cats in cold houses burn a little more energy keeping warm, while cats in warm flats in summer may eat a little less. These are small effects compared with portion size and play. If your cat weight is steady, do not chase seasonal changes with constant adjustments. A stable routine, weighed portions, and a monthly weigh-in will do far more than any complicated schedule.
To sum up, indoor feeding is about matching a quieter life with a smaller bowl. Weigh the cat, weigh the food, keep treats inside the total, and add play to the day. This calculator gives you the starting number. The scale tells you whether it is right, and small adjustments every few weeks keep it right for years.