Resting Energy Requirement (RER) represents the calories needed to maintain basic metabolic functions in a thermoneutral environment at rest. The standard formula used in veterinary medicine is: RER = 70 × (body weight in kg)^0.75
This exponential relationship reflects the fact that metabolic rate does not scale linearly with body mass. Smaller animals have higher metabolic rates per kilogram. A 5 kg cat has a higher RER per kg than a 25 kg dog.
| Weight (kg) | RER (kcal/day) |
|---|---|
| 2 | 118 |
| 5 | 234 |
| 10 | 394 |
| 20 | 662 |
| 30 | 897 |
RER must be multiplied by a factor reflecting the patient's life stage, activity level, and physiological state. These DER multipliers transform resting needs into actual daily caloric requirements. Use the Calorie (RER) Calculator for quick calculations.
| Life Stage | DER Multiplier |
|---|---|
| Neutered adult | 1.2–1.4 |
| Intact adult | 1.4–1.6 |
| Active/working dog | 1.6–2.0 |
| Pregnancy (late) | 1.6–2.0 |
| Lactation | 2.0–4.0 |
| Growth (puppy/kitten) | 2.0–3.0 |
| Senior, sedentary | 1.1–1.3 |
| Weight loss | 0.8 × RER |
Always assess Body Condition Score (BCS) before calculating calories with the Body Condition Scorer. A BCS 6/9 dog needs fewer calories than the standard multiplier suggests. For weight loss, start at 0.8 × RER and reassess every 2–4 weeks. Aim for 1–2% body weight loss per week in dogs, 0.5–1% in cats to avoid hepatic lipidosis.
For overweight patients, reduce the multiplier by 0.2–0.4. For underweight patients or those with high metabolic demand, use the upper end of the range.
Measure food with a standard measuring cup or kitchen scale. Feeding guidelines on bags are estimates for intact, active adults—most pets need less. Split daily intake into 2 meals to reduce begging behavior and improve satiety. Avoid free-feeding in obesity-prone breeds and neutered animals.
Consider therapeutic weight management diets with increased fiber and protein when standard calorie restriction fails. These promote satiety while preserving lean body mass.
Seek veterinary guidance for pets with unexplained weight gain or loss, concurrent disease (diabetes, hypothyroidism, hyperadrenocorticism), or when standard calculations do not achieve desired outcomes. Some conditions significantly alter energy requirements.
- RER = 70 × (body weight in kg)^0.75
- Apply DER multipliers for life stage, activity, and physiological state.
- Weight loss: start at 0.8 × RER; aim for 1–2% body weight loss/week in dogs.
- Assess BCS before calculating calories.
- Split daily intake into 2 meals; avoid free-feeding in obesity-prone pets.