Cat Food Calculator
Calculate your cat's daily calorie needs and portion sizes from weight, life stage and activity — for wet food, dry food or both. Free tool.
How the calculation works
Cats are not small dogs, and their feeding maths reflects that. They are obligate carnivores with a narrow energy range, they are much smaller — so a 20 kcal error matters far more — and their multipliers sit well below canine ones. A neutered indoor cat runs on roughly a tenth of what a working retriever needs.
Step 1 — Resting energy requirement (RER)
RER (kcal/day) = 70 × (body weight in kg)^0.75For a 4 kg (8.8 lb) cat that is about 198 kcal at complete rest.
Step 2 — The life-stage multiplier
| Situation | × RER |
|---|---|
| Kitten, under 4 months | 2.5 |
| Kitten, 4–12 months | 2.0 |
| Neutered adult | 1.2 |
| Intact adult | 1.4 |
| Inactive / obese-prone | 1.0 |
| Senior, 11+ years | 1.1–1.6 |
| Weight loss (on ideal weight) | 0.8 |
Notice how tight the adult band is. The gap between an intact and a neutered cat is about 17% — for a 4 kg cat, roughly 40 kcal, or a little under half a small can. That is why neutered indoor cats gain weight so readily when nothing about their bowl changes.
The senior reversal
Energy needs fall through middle age and then climb again. From around eleven years, many cats digest fat and protein less efficiently, so more food has to go in to deliver the same usable energy. The practical consequence is that the classic advice — older animal, less food — is wrong for cats often enough to be dangerous. Weight loss in an older cat is a clinical sign, not a success: hyperthyroidism, chronic kidney disease and diabetes all present that way. Our guides on hyperthyroidism and feline diabetes cover what else to watch for.
Why feline weight loss has its own rules
Cats can develop hepatic lipidosis — fatty liver — when they go into a sharp energy deficit. Fat floods to a liver that cannot keep up, and the condition can become life-threatening within days. Overweight cats are the most susceptible, which makes crash dieting exactly the wrong response to obesity in this species. A safe plan holds at about 0.8 × RER of the target weight, aims for no more than 0.5–1% of body weight per week, and is monitored by a vet. If a cat on a diet stops eating altogether, that is an urgent problem, not a plateau.
Wet, dry, or both
The calculator works in calories and then converts, because volume comparisons between wet and dry food are meaningless — a 5.5 oz can might carry 170 kcal while a cup of kibble carries 350. If you feed both, it splits the target evenly and gives you the amount of each; adjust the ratio to taste as long as the calories add up. Wet food's real advantage is water content, which matters for a species that drinks reluctantly and is prone to urinary problems. Our full comparison of wet versus dry food goes through the trade-offs.
Checking against the cat in front of you
Feel along the ribs: they should be findable under a thin fat covering without pressing hard. Look down from above for a waist behind the ribs, and from the side for a slight abdominal tuck. A primordial pouch — the loose flap of skin along the belly — is normal anatomy in many cats and not a sign of obesity. Weigh monthly on the same scale; a 200 g change in a 4 kg cat is 5% of body weight, which is substantial.
Common questions
- How much should I feed my cat per day?
- Most neutered indoor adult cats land somewhere between 180 and 260 kcal a day, but that range is wide enough to be useless without knowing the individual cat. The figure depends mainly on lean body weight, neuter status and how active the cat actually is: a 4 kg (9 lb) neutered cat that mostly sleeps needs about 200 kcal, the same cat playing daily around 240, and intact with outdoor access closer to 315. Calculate from your own cat rather than from an average.
- Do senior cats need less food?
- This is the one place the dog rules get reversed, and it catches a lot of owners out. Cats reduce their energy needs through middle age, but from roughly eleven years onward many lose the ability to digest fat and protein efficiently — so their calorie requirement climbs again even as their appetite may fall. A significant share of cats over twelve are underweight rather than overweight. If an older cat is losing weight, that is a reason to see a vet, not a reason to relax.
- Why must a cat lose weight so slowly?
- Because cats are uniquely vulnerable to hepatic lipidosis — fatty liver disease. When a cat goes into a sharp calorie deficit, body fat mobilizes faster than the liver can process it, and the liver becomes overwhelmed. It can develop within days of a cat barely eating, it is life-threatening, and overweight cats are the most at risk. A feline weight-loss plan should never cut below about 80% of the resting requirement, should target no more than 0.5–1% of body weight per week, and should be supervised by a vet. Never simply stop feeding an overweight cat.
- Should I feed wet food, dry food, or both?
- Either can be complete and balanced, so the practical differences matter more than the ideology. Wet food carries far more water, which supports urinary health in a species that evolved to get most of its moisture from prey and drinks poorly by choice. Dry food is cheaper per calorie, keeps better in the bowl, and suits puzzle feeders. Many owners land on both. Whichever you choose, work in calories — a 5.5 oz can and a cup of kibble are nowhere near equivalent.
- Is free-feeding bad for cats?
- Leaving dry food out permanently is the most common reason indoor cats become overweight: a neutered indoor cat needs remarkably little food, and grazing all day quietly exceeds it. Cats do naturally eat many small meals, so the answer is not necessarily fewer meals — it is a measured daily amount, portioned out or delivered through a timed feeder or puzzle toy, rather than a bowl topped up whenever it looks low.