Cat Food Portion Calculator
Calculate how much to feed your cat per day based on body weight and neutering status using the feline RER formula.
How to use this tool
- Weigh your cat, ideally on the same scales at the same time of day.
- Select your cat's neutering status (neutered cats need ~20% fewer calories).
- Enter the energy density from the food packaging (kcal per 100 g).
- The result shows recommended daily grams and the calorie breakdown.
Use this calculator to find the right daily food amount for your cat based on body weight and neutering status.
Not veterinary advice. These results are estimates for general guidance only. Always consult a licensed veterinarian before making health, nutrition, or medication decisions for your pet.
Formula
Resting Energy Requirement: RER = 70 × weight(kg)0.75 kcal/day
Maintenance Energy Requirement: MER = RER × status_factor
Status factors: neutered 1.2 · intact 1.4 · kitten 2.5 · obese 0.8
Daily food: grams/day = MER ÷ kcal_per_100g × 100
How it works
The calculator applies the standard feline RER formula (70 × BW0.75) to estimate baseline calorie needs, then adjusts for neutering status using multipliers grounded in veterinary nutrition guidelines. Neutered cats have a lower energy requirement than intact cats, kittens need significantly more to support growth, and obese cats are assigned a reduced factor to promote safe weight loss.
The gram result is derived by dividing daily calorie needs by the food's energy density. Wet and dry foods differ substantially in energy density, so entering the correct kcal/100 g value from the food label is important for accuracy.
Worked example
Worked example
- Cat weight = 4 kg, status = neutered (factor 1.2), food energy = 350 kcal/100 g.
- RER = 70 × 4^0.75 = 70 × 2.828 ≈ 198 kcal/day.
- MER = 198 × 1.2 = 238 kcal/day.
- Food per day = 238 ÷ 350 × 100 ≈ 68 g/day.
RER 198 kcal/day, MER 238 kcal/day, 68 g/day
Key terms
- RER (Resting Energy Requirement)
- The minimum calories needed to sustain vital functions at rest; for cats calculated as 70 × BW(kg)^0.75.
- Neutering status factor
- A multiplier reflecting how reproductive status and life stage affect a cat's calorie needs; neutered cats need fewer calories than intact cats due to hormonal and metabolic changes.
- Metabolic scaling (BW^0.75)
- Energy expenditure scales with the 3/4 power of body mass because larger animals have proportionally less surface area and lower mass-specific metabolic rates.
- Energy density (kcal/100 g)
- Calories per 100 g of food; dry kibble is typically 300–400 kcal/100 g, while wet food is often 70–120 kcal/100 g.
- Obesity factor (0.8)
- A below-maintenance multiplier used to create a calorie deficit for overweight cats while still meeting minimum nutritional needs.
Frequently asked questions
- How many calories does a cat need per day?
- A typical neutered adult cat (4 kg) needs roughly 200–240 kcal/day. Kittens need up to 2.5× more calories per kg to support growth.
- Should I feed wet or dry cat food?
- Both can be nutritionally complete. Wet food has higher moisture content which supports kidney health. Always check the energy density on the packaging and adjust portion sizes accordingly.