How many calories does your cat need?
Personalised, life-stage adjusted, and tuned for the way cats actually metabolise — with a safer weight-loss plan than dog calculators offer (cats can develop fatty liver from aggressive deficits, so this matters).
MER = (70 × weight_kg^0.75) × cat-specific multiplier Same RER formula as dogs. Cat multipliers are notably lower (1.2× for a neutered indoor adult vs 1.6× for the same dog).
Cat calorie needs calculator
Personalised, life-stage adjusted, and tuned for the way cats actually eat — low maintenance multipliers, a safer weight-loss plan, and a note about hepatic lipidosis you should know before restricting calories.
Selected: Ideal — ideal is 4–5 / 9.
That's about 0.5 cups of dry food.
±15% individual variation — verify with body condition score over 4–6 weeks.
How this number was calculated
Step 1 — Resting Energy Requirement (RER). The baseline calories your cat burns at rest. RER = 70 × W(kg)0.75.
For your cat: 4.5 kg → RER = 0 kcal/day.
Step 2 — Maintenance Energy Requirement (MER). RER × a cat-specific multiplier.
For your cat: —.
Final: RER × multiplier = 0 kcal/day.
Source: NRC Nutrient Requirements of Dogs and Cats (2006); AAFP/AAHA Feline Life Stage Guidelines (2021).
Quick answer
A neutered adult indoor cat needs roughly 1.2 × RER, where RER
("Resting Energy Requirement") is 70 × weight(kg)0.75.
For a 4.5 kg (10 lb) neutered indoor adult that's about 270 kcal/day —
roughly 0.7 cups of dry food or 3 small cans of wet food.
Cats use significantly fewer calories per pound than dogs, mostly because they sleep 16+ hours a day and don't go on walks. The biggest lever for adjustment is activity — outdoor and athletic-indoor cats can need 30–40% more.
The two-step method (RER × MER)
The RER formula 70 × W(kg)0.75 is identical to dogs — it's an
allometric law that holds across all placental mammals. What changes is the multiplier
that converts resting needs into daily needs.
For cats, the standard NRC / AAFP multipliers are:
| Situation | × RER |
|---|---|
| Kitten, under 4 months | 2.5 |
| Kitten, 4 months to 1 year | 2.0 |
| Intact adult cat | 1.4 |
| Neutered adult, typical indoor | 1.2 |
| Senior cat (11–14) | 1.1 |
| Geriatric cat (15+) | 1.0 |
| Active / outdoor adult | +0.2 to +0.4 |
| Weight-loss plan (target weight) | 0.8 |
Why cat weight-loss plans are different
Cats have a unique metabolic vulnerability: hepatic lipidosis, or fatty-liver disease. When a cat doesn't get enough calories, its body breaks down stored fat for energy — and the liver gets flooded with more fat than it can process. The fat accumulates in liver cells, the liver fails, and untreated cases are often fatal.
This is why cat calorie-restriction plans must be slower than dog plans. The calculator uses 0.8 × RER for goal weight as the starting point — conservative by design. Target 0.5–1% body weight loss per week. If your cat refuses to eat the restricted ration, do not let her go more than 24 hours without food (12 hours if pregnant or lactating). Cats that stop eating can develop hepatic lipidosis within 48–72 hours even at a healthy weight. Consult your vet before starting a weight-loss plan.
Free-feeding is the leading cause of cat obesity
Most pet cats with weight problems share the same feeding pattern: a bowl of kibble constantly available, "refilled when low." This is a structural problem, not a willpower problem. Cats evolved as solitary hunters that ate 8–10 small prey per day; their satiety signalling was tuned for low-energy-density meals spaced throughout the day. Modern dry kibble is energy-dense and palatable in a way no prey item ever was — the satiety signal can't keep up.
The single most effective intervention is to switch to measured meals: 2–3 daily portions weighed against the calculator's recommendation. Puzzle feeders and slow-feed bowls help further by adding cognitive load to eating, which suppresses the speed-fed binge response.
Activity level — how to choose
- Low: typical indoor cat. Sleeps 16+ hours a day. Plays in short bursts. This is the default — most pet cats fit here.
- Moderate: plays daily, uses a cat tree or climbs reliably, kept lean by enrichment.
- Active: outdoor access, hunts, or genuinely athletic indoor (think working farm cats or feral / outdoor colonies).
Common myths
"Cats self-regulate intake." Some cats do. Most don't, especially neutered cats with dry food. The obesity epidemic in housecats is the evidence.
"Wet food is fattening because it's wet." Wet food is mostly water (75–80%) and is lower in calories per gram than dry. Switching from dry to wet usually reduces total intake.
"All cats need fish-based food because they're carnivores." Cats need animal protein, but fish has high levels of thiaminase and mercury and isn't a natural cat prey item. Chicken, turkey, and rabbit are biologically more appropriate. Variety matters.
"Senior cats don't need to eat much." Senior cats often need more protein per pound, not less, to maintain lean mass. Calories drop modestly; protein percentage should rise.
Sources: National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press (2006). AAFP / AAHA Feline Life Stage Guidelines (2021). AAHA Weight Management Guidelines for Dogs and Cats (2014; reaffirmed 2021). Armstrong PJ, Blanchard G. "Hepatic lipidosis in cats." Vet Clin North Am Small Anim Pract. 2009.
Frequently asked questions
How many calories does my cat need per day?
It depends on weight, life stage, neuter status, and activity level. A typical neutered adult indoor cat needs roughly 1.2 × their Resting Energy Requirement (RER), where RER = 70 × bodyweight in kg to the 0.75 power. A 4.5 kg (10 lb) neutered indoor adult therefore needs about 270 kcal/day. Use the calculator above for your cat's specific numbers.
Why are cat MER multipliers lower than dogs?
Cats are smaller, generally less active, and spend more time sleeping. The typical neutered indoor cat uses 1.2 × RER vs the typical neutered adult dog at 1.6 × RER. This is despite both species using the same allometric RER formula. Failing to account for this difference is why dog-feeding intuitions over-feed cats — and obesity is now the most common nutritional disorder in housecats.
My cat is overweight. How do I help her lose weight safely?
Slowly. Aggressive calorie restriction in cats can trigger hepatic lipidosis (fatty liver), a potentially fatal condition where the liver becomes overwhelmed processing mobilised fat. The calculator uses 0.8 × RER for the cat's target (ideal) weight as a starting point — this is conservative by design. Target 0.5–1% body weight loss per week (slower than dogs). Weigh weekly. Never let your cat skip meals: cats that stop eating for 24–48 hours can develop fatty liver even at a healthy weight. Consult your vet before starting a weight-loss plan, especially for cats over 9 lb (4 kg) overweight.
What is hepatic lipidosis and why should I care?
Hepatic lipidosis (fatty liver disease) is the most common liver disease in cats. It develops when a cat doesn't eat enough — the body starts breaking down body fat for energy, and the liver gets flooded with more fat than it can process. The fat accumulates in liver cells, the liver fails, and untreated cases are often fatal. Overweight cats and cats that have stopped eating are at highest risk. This is why cat weight-loss plans are slower than dog plans, and why "my cat won't eat" is always a medical concern.
Does indoor vs outdoor change calorie needs?
Yes, but less than you might think. An "active" outdoor cat or athletic indoor cat (lots of climbing, hunting, structured play) uses about 1.4–1.8 × RER (intact athletic cats reach ~1.8) vs the 1.2 × RER baseline for a typical neutered indoor cat. The bigger difference is lifespan — outdoor cats live half as long on average — and food intake is rarely the limiting factor in either case. Use the calculator's "active" setting if your cat has outdoor access or genuinely athletic indoor habits.
How accurate is this for kittens?
Reasonable for general feeding, but kittens grow fast and need recalculation every 2–3 weeks. The calculator uses 2.5 × RER for kittens under 4 months and 2.0 × RER from 4 months to 1 year. Feed kitten-formulated food, not adult food — kittens have higher protein, calcium, and DHA requirements that adult formulas don't meet. Large-breed cats like Maine Coons grow more slowly; consider keeping them on kitten food until 18 months.
How do I convert calories to cups or cans of food?
The calculator shows approximate cups of dry food (~400 kcal/cup average for cat kibble — denser than dog kibble) and cans of wet food (~85 kcal per standard 3 oz / 85 g pâté can). Real values vary a lot — premium and weight-management formulas can be 250–350 kcal/cup, while kitten food can hit 500+. Always read the calorie density on your specific food. The "ME" (metabolisable energy) is what matters.
My cat free-feeds (kibble always available). Is that wrong?
For most cats, yes — free feeding is the leading cause of feline obesity. Cats domesticated from solitary hunters that ate 8–10 small meals per day, and free access to high-energy kibble overrides their natural satiety. Meal feeding (2–3 measured meals per day) is the single most effective change for weight control. Puzzle feeders and slow-feed bowls help by adding cognitive load to the meal — they're especially good for cats who eat too fast and vomit.
What is body condition score (BCS) and how do I check it on a cat?
BCS for cats uses a 1–9 scale: 4–5 is ideal. To check: (1) Run your hands along the cat's ribs — you should feel them easily with light pressure, with a thin fat layer over them. (2) View from above — you should see a visible waist behind the ribs. (3) View from the side — the belly should tuck up slightly toward the back legs. If ribs are hard to find, your cat is over-conditioned (BCS 6+); if ribs are visible without touching, under-conditioned (BCS 3 or lower). BCS is more reliable than weight alone because it accounts for muscle vs fat.
My senior cat is losing weight on the same diet. Should I just feed more?
Get to a vet first. Unintentional weight loss in older cats has three common medical causes: hyperthyroidism (very common), chronic kidney disease, and diabetes mellitus. All three can present as a cat that eats normally — or more than normal — but still loses weight. A simple blood and urine panel screens for all three. Adding calories won't fix a medical problem and can mask it.