Pet Resting Energy Requirement Calculator
Resting energy requirement (RER) is the foundation of pet feeding calculations. The standard veterinary formula scales with metabolic body size: RER equals 70 times body weight in kilograms raised to the power 0.75. This calculator returns the RER and then multiplies it by a life-stage or activity factor you choose to give an estimated daily maintenance calorie target. The activity factor is a user-editable input so you can match your animal's life stage and your veterinarian's advice.
RER formula
RER (kcal/day) = 70 * (weight in kg)^0.75
Daily maintenance energy = RER * activity factor
The exponent 0.75 reflects metabolic body size. Multiplying RER by an activity or life-stage factor gives the daily maintenance target.
Worked example
A 15 kg dog with a 1.6 activity factor: RER = 70 * 15^0.75 = 70 * 7.62199 = 533.54 kcal/day. Daily maintenance energy = 533.54 * 1.6 = 853.66 kcal/day.
Resting energy: frequently asked questions
What is resting energy requirement?
Resting energy requirement (RER) is the calories an animal needs at rest in a thermoneutral environment to maintain basic body functions. The standard allometric formula is RER in kcal per day equals 70 times body weight in kilograms raised to the power 0.75.
How do I get daily calories from RER?
Maintenance energy requirement (MER) is RER multiplied by a life-stage or activity factor. Typical factors range from about 1.2 for an inactive neutered adult to 2.0 or higher for active, growing or lactating animals. This calculator keeps the factor as a user-editable input.
Does this apply to both cats and dogs?
The RER formula applies to both, since it is based on metabolic body size. The activity factor differs between species and life stages, so enter the value appropriate to your individual animal as advised by your veterinarian.
Official sources
- U.S. National Academies, National Research Council: Nutrient Requirements of Dogs and Cats (metabolic energy requirements).
- The 70 times weight to the 0.75 power relationship is the standard allometric metabolic-rate scaling.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.