Cat Calorie Calculator (RER and DER)
Calculate Resting Energy Requirement (RER) and Daily Energy Requirement (DER) for a cat. RER is the calories needed at rest in a thermoneutral environment; DER adjusts for activity, life stage, and reproductive status.
Species
Body weight
Life stage / activity
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For trained veterinary professionals. Check every result against current drug labels, your formulary, and the patient before acting on it. This tool is not veterinary advice. Clinical disclaimer
How to use this tool
The formulas
RER = 70 × (body weight in kg)0.75 - the metabolic-weight calculation. Works for cats between 2 and 15 kg.
DER = RER × life-stage factor. Typical factors for cats:
- Adult, neutered: 1.2
- Adult, intact: 1.4
- Weight loss target: 1.0 × RER for ideal body weight
- Weight gain target: 1.7-2.0 × RER
- Kitten / growth: 2.5
How to apply it
Convert the DER to grams of food using the kcal density listed on the diet's label (most labels list kcal/cup or kcal/can). For weight loss, target the ideal body weight, not the current weight, and recheck every 2-4 weeks.
Frequently asked questions
How many calories does my cat need a day?
Start with RER = 70 × body weight (kg)^0.75, then multiply by a life-stage factor - commonly 1.2 for a neutered adult, 1.4 for an intact adult, 2.5 for a kitten.
How many calories should an overweight cat eat to lose weight?
For weight loss, apply the factor (commonly around 1.0) to the ideal body weight, not the current weight - using current weight in an overweight cat overestimates the calorie target.