About This Calculator

This calculator estimates your resting metabolic rate (or RMR). Your resting metabolic rate is the the amount of calories that your body burns while you are at complete rest (i.e. reclining with muscles relaxed) to keep itself alive and digest food, but nothing else. More specifically, resting metabolic rate calories are burned to digest, absorb, and store the nutrients in the food you've eaten (you can read more about this in the Thermic Effect of Food article), and to sustain the function of vital organs like your heart, brain, nervous system, lungs, kidneys, liver, muscles, and skin. Resting metabolic rate does not account for calories burned to support physical activity. Anything done throughout the day, apart from simply resting with complete muscular relaxation, requires calories to be burned in addition to those burned to support resting metabolic rate.

It should be noted that resting metabolic rate is not the same as basal metabolic rate (or BMR). There is a slight difference between the two, in that a resting metabolic rate estimation includes consideration for calories burned to digest food, whereas basal metabolic rate does not. For this reason, your resting metabolic rate is typically considered to be a more reliable estimation of your calorie burn during rest than basal metabolic rate, because your body is usually digesting some amount of food at any given moment. For example, to perform a typical basal metabolic rate measurement in a laboratory setting a subject would need to have fasted for 12 to 14 hours, whereas no fasting is required for a resting metabolic rate measurement.

This calculator is based on the widely used and accepted Harris-Benedict equations for determining basal metabolic rate BMR, with a modification incorporated to account for calories burned to support digestion of food. The basal metabolic rate estimates are simply increased by 10% (representing additional calorie burn required to digest food) to arrive at a resting metabolic rate estimate. You can read more about where the 10% factor comes from in the Thermic Effect of Food article. The formulas are shown below:

Calculator Formulas

• Male (metric): RMR = [(13.75 x WKG) + (5 x HC) - (6.76 x age) + 66] x 1.1
• Male (imperial): RMR = [(6.25 x WP) + (12.7 x HI) - (6.76 x age) + 66] x 1.1
• Female (metric): RMR = [(9.56 x WKG) + (1.85 x HC) - 4.68 x age) + 655] x 1.1
• Female (imperial): RMR = [(4.35 x WP) + (4.7 x HI) - 4.68 x age) + 655] x 1.1

where

HC = Height in Centimetres
HI = Height in Inches
WKG = Weight in Kilograms
WP = Weight in Pounds

Reference

Harris JA and Benedict FG. A Biometric Study of Human Basal Metabolism. Proc Natl Acad Sci U S A. 1918 December; 4(12): 370-373.