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Resting Energy Requirement Calculator

Calculate resting energy requirement for dogs and cats. Free veterinary calorie requirements tool for veterinary, calorie, and more.

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Inputs that matter
Body Weight, MER Factor
Output to expect
Resting Energy Requirement Calculator
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Exponential RER Formula (Preferred)

The current standard uses an allometric equation validated across body weights: RER = 70 × (body weight in kg)^0.75. This replaces the linear 30 × weight + 70 formula for animals over 2 kg.

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

Linear RER Formula (Legacy)

For animals between 2–45 kg, the simplified linear formula RER = 30 × weight(kg) + 70 provides similar results and is still widely used in clinical practice.

RER (kcal/day) = 30 × Weight (kg) + 70

Daily Energy Requirement Multipliers

DER = RER × life-stage factor. Neutered adult dog: 1.6×. Active dog: 2.0–5.0×. Indoor cat: 1.2×. Kitten growth: 2.5×. These multipliers convert resting needs to actual feeding requirements.

DER = RER × Life-Stage Factor

Updated: July 2026

Example Scenarios

Typical indoor spayed female medium breed with normal activity.

Weight: 15 kgSpecies: DogLife Stage: Neutered adult (×1.6)

→ RER ≈ 534 kcal/day; DER ≈ 854 kcal/day

Border collie with daily herding work and training sessions.

Weight: 30 kgSpecies: DogLife Stage: Active/working (×3.0)

→ RER ≈ 897 kcal/day; DER ≈ 2,691 kcal/day

Neutered indoor cat with minimal activity and no outdoor access.

Weight: 4.5 kgSpecies: CatLife Stage: Indoor neutered (×1.2)

→ RER ≈ 218 kcal/day; DER ≈ 262 kcal/day

Common Mistakes to Avoid

Feeding RER instead of DER

RER is resting metabolism only. Feeding RER to an active dog causes weight loss; feeding RER to a sedentary cat may still be too much if the multiplier is not applied correctly. Always multiply RER by the appropriate life-stage factor.

Using ideal weight instead of current weight for obese pets

For weight loss plans, calculate RER based on ideal weight, not current weight. Using current weight of an obese pet overestimates caloric needs and slows weight loss progress.

Applying dog multipliers to cats

Cats have lower activity multipliers (1.0–1.4× for most adults) compared to dogs (1.4–1.6× for neutered adults). Using dog factors for cats leads to overfeeding and obesity.

FAQ

RER (Resting Energy Requirement) is baseline metabolism at rest. MER (Maintenance Energy Requirement) equals DER — the actual daily calories needed including activity and thermoregulation. MER = RER × life-stage multiplier.

Calculate RER using ideal body weight, then feed 70–80% of the neutered adult DER (RER × 1.4 × 0.75). Monitor weight every 2 weeks and adjust by 10% if loss exceeds 2% body weight per week.

The allometric exponent (0.75) means smaller animals have higher mass-specific metabolic rates. A 3 kg dog needs ~180 kcal/day (60 kcal/kg) while a 30 kg dog needs ~897 kcal/day (30 kcal/kg).

RER formulas predict energy needs within 10–20% for healthy animals. Individual variation in activity, metabolism, and neuter status requires monitoring body condition score (BCS) and adjusting intake every 2–4 weeks.

Yes. Growing puppies and kittens need 2.0–3.0× RER. Senior pets often need 10–20% fewer calories due to reduced activity. Recalculate when transitioning life stages or after neutering.

About Resting Energy Requirement Calculator

Resting Energy Requirement (RER) is the baseline caloric need for a healthy, resting animal at thermoneutral temperature. Veterinarians use RER as the foundation for calculating Daily Energy Requirement (DER) by applying life-stage and activity multipliers for feeding plans.