Free Online Cat Food Calculator

Wondering how much should I feed my cat calculator-style, without doing the maths yourself? This cat food calculator works out how much to feed a cat by weight (kg) or pounds, using your cat's life stage and your food's calories per cup. Use this cat feeding calculator to get a daily kcal target and a cups-per-day serving size based on the veterinary RER/MER formula.

Looking to calculate food portions for your canine friend? Head over to our Dog Food Calculator to easily estimate your dog’s daily calorie needs and meal size.

Cat Food Calculator

kcal / cup

Life Stage Reference

These are the RER multipliers this calculator uses for each life stage, based on standard veterinary nutrition references.

Life StageMultiplier (× RER)
Weight Loss (Overweight)0.8
Senior (7+ years)1.1
Neutered Adult (Typical)1.2
Intact Adult1.4
Weight Gain1.2–1.8
Kitten (4–12 months)1.6–2.0
Kitten (Under 4 months)2.5
Pregnant / Nursing Queen2.5

Your Results

Your cat's daily calorie needs and recommended cups per day will appear here once you calculate.

How Much Should I Feed My Cat? The Formula Explained

Cats are true carnivores with a metabolism that behaves quite differently from dogs, so a generic "cups per day" line on a food bag rarely fits an individual cat. A more reliable way to work out how much to feed a cat by weight (kg) is to calculate its baseline resting energy need, then scale that up using a life-stage multiplier before converting it into an actual serving size.

Step 1: Resting Energy Requirement (RER)

RER is the number of calories a cat would burn simply lying still — breathing, digesting, keeping organs running. It's calculated from body weight using the same metabolic-scaling formula recommended in veterinary nutrition references, including the WSAVA Global Nutrition Committee Guidelines and Mark Morris Institute's Small Animal Clinical Nutrition (5th ed.):

RER (kcal/day) = 70 × (Weight in kg) ^ 0.75

Step 2: Maintenance Energy Requirement (MER)

RER alone assumes total rest, so it's multiplied by a life-stage factor that accounts for growth, reproduction, neuter status and weight goals, giving the cat's actual daily calorie need:

MER (kcal/day) = RER × Life Stage Factor

That factor ranges from as low as 0.8 for a cat on a supervised weight-loss plan, up to 2.5 for a nursing queen or a very young kitten — see the full reference table alongside the calculator above.

Step 3: Converting Calories to Cups

Finally, divide the daily calorie requirement by your specific food's calories per cup (usually printed on the bag or can as kcal/cup) to get the actual serving size:

Cups per day = MER (kcal/day) ÷ Calories per cup

Worked Example

Say you have a 4.5kg neutered adult cat (factor 1.2), fed a food with 300 kcal per cup:

Step 1: RER = 70 × 4.50.75 = 70 × 3.09 = 216 kcal/day
Step 2: MER = 216 × 1.2 = 260 kcal/day
Step 3: 260 ÷ 300 = 0.87 cups/day

A Few Important Notes Before You Feed

  • Indoor, neutered cats — the majority of pet cats — are the most common life stage, and also the ones most prone to obesity, since their calorie needs are lower than the guidelines printed on most packaging.
  • This calculator assumes you feed the full daily amount across the day; if you split meals, divide the total cups by the number of meals.
  • Reducing calories too fast in an overweight cat can trigger a serious liver condition called hepatic lipidosis — never cut more than about 20–25% below maintenance without veterinary supervision.
  • Kittens, pregnant or nursing queens, and cats with a medical condition all have needs that can vary significantly from these general estimates, so check with your veterinarian before relying on this figure alone.

Frequently Asked Questions (FAQs)

Yes, there are dedicated kitten life-stage options, but treat the result as a rough starting point only. Kittens grow fast and their needs change month to month, so always check your kitten food's own feeding chart and your vet's guidance alongside this calculator.

Neutering lowers a cat's metabolic rate, so a neutered adult typically needs noticeably fewer calories (factor 1.2) than an intact adult of the same weight (factor 1.4). This is one reason neutered indoor cats are especially prone to gaining weight if fed like an intact cat.

Weigh out one cup of the food on a kitchen scale, then use the calories-per-kg figure to work out the calories in that exact cup weight. Enter that number into the calculator as the calories per cup.

Cats in these categories cover a wide spread of individual needs, so the calculator gives a low-to-high range instead of a single figure. Start near the lower end and adjust upward if your cat isn't gaining or growing as expected.

Roughly every 2 to 4 weeks, or any time your cat's weight, life stage, or food brand changes. Re-weigh your cat and re-run the calculator so the serving size keeps matching its current needs.
Disclaimer: This calculator provides a general estimate based on the standard RER/MER veterinary energy-requirement formula referenced by WSAVA and Mark Morris Institute's Small Animal Clinical Nutrition, and is not a substitute for advice from a licensed veterinarian. Every cat is different — use this figure as a starting point, monitor your cat's body condition regularly, and consult your vet for any health concerns or before making significant changes to their diet.

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