When you want to plan a dog's diet precisely, it is not enough to glance at the table on the packaging. Veterinarians use two concepts: RER, the resting energy requirement, and MER — the requirement for an animal leading a normal, active life. Understanding both lets you calculate calories with a precision that general guidelines cannot offer.
What is RER?
RER (Resting Energy Requirement) is the amount of energy the body needs at rest — to maintain basic life functions, without movement or work. It is calculated with the formula:
- RER = 70 × (body weight in kg) raised to the power of 0.75
The power of 0.75 is so-called metabolic scaling — it reflects the fact that metabolism does not grow linearly with body weight. A small dog uses proportionally more energy per kilogram than a large one.
What is MER?
MER (Maintenance Energy Requirement) is RER multiplied by a factor for activity and physiological state. The most commonly used multipliers are:
- Neutered adult dog, low activity: 1.6
- Intact adult dog: 1.8
- Overweight dog (weight loss): 1.0–1.4
- Active / working dog: 2.0–5.0
- Puppy up to 4 months: 3.0
- Lactating bitch: 4.0–8.0
Example: a 20 kg dog, neutered, low activity
- First the power: 20 raised to the power of 0.75 = about 9.46
- RER = 70 × 9.46 = about 662 kcal
- The MER factor for a neutered, low-activity dog = 1.6
- MER = 662 × 1.6 = about 1059 kcal per day
This is the real daily energy requirement of such a dog. With this number and the calorie content of the food, it is easy to choose the portion — just divide the MER by the calorie content per gram.
Why this matters
Two dogs of the same weight can have wildly different requirements. A shepherd dog working in the field burns up to three times as much as a neutered dog sleeping on the sofa. Using a single portion for both would lead to malnutrition in one and obesity in the other.
Note: the RER and MER formulas give approximate values for healthy dogs. This is not veterinary advice — for metabolic diseases, pregnancy or recovery, set the requirement together with a veterinarian.
Calculate the food portion based on the requirement: Dog food calculator →