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Pet Resting Energy (RER)

Find your pet's daily resting energy requirement (RER).

How it is calculated

The tool uses the exponential veterinary formula RER (kcal/day) = 70 × weight^0.75, where weight is the animal's body weight in kilograms. The power 0.75 means energy need grows more slowly than weight: doubling the weight raises RER by about 68 %, not 100 %. That is why a 4 kg cat and a 40 kg dog differ by about 9 times in weight but only by about 5.6 times in energy. The result is rounded to a whole kcal. The number is the energy for resting only. It is not the feeding amount, because real daily need is RER multiplied by a factor for age, activity and condition, and the tool does not apply that factor. Zero or negative weights give no result.

Worked example

A dog weighs 10 kg. Raise the weight to the power 0.75: 10^0.75 = 5.623. Multiply by 70: 70 × 5.623 = 393.6, shown as 394 kcal per day. If that dog is a typical indoor adult, the guide texts use a factor of roughly 1.2 to 1.4, which would put its daily need near 470 to 550 kcal. Compare a 5 kg dog: 5^0.75 = 3.344, so RER is 234 kcal, not half of 394.

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Common mistakes

  • Feeding exactly the RER figure. It is the resting energy, so most active adult pets need more once an activity factor is applied, and a pet being slimmed needs a different factor.
  • Entering weight in pounds. The field is kilograms, so a 22 lb dog is about 10.
  • Expecting the energy to double when the weight doubles. Because of the 0.75 power it rises by about 68 %, so you cannot scale a small pet's figure linearly.
  • Using an overweight pet's current weight to set a diet. The result then supports the extra weight; vets usually work from the ideal weight instead.
  • Treating the figure as a food amount. It is in kcal per day, so you still need the kcal per cup or per gram of your food to get a portion.

About this calculator

Resting Energy Requirement (RER) is the number of calories a dog or cat burns at complete rest just to keep basic body functions running, calculated from the widely used veterinary formula RER = 70 × (body weight in kg)^0.75. It is the foundation figure that every other feeding calculation in veterinary nutrition builds on top of.

Veterinarians and veterinary nutritionists multiply RER by a life-stage or activity factor — roughly 1.2 to 1.4 for an average indoor adult, higher for growing puppies and kittens, lactating animals or working dogs, and lower for weight loss or a sedentary senior pet — to arrive at the actual Maintenance Energy Requirement (MER) used to set a daily feeding amount. Pet food labels and prescription weight-management diets are formulated around exactly this RER-then-multiplier logic, which is why vets ask for a pet’s weight before recommending how much of a given food to feed per day.

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