Resting metabolic rate (RMR) is the amount of energy that your body burns while at rest. It is the total number of calories burned when your body is completely at rest, supporting breathing, circulating blood, organ functions, and basic neurological functions. RMR differs from basal metabolic rate (BMR) because BMR measurements must meet total physiological equilibrium, whereas RMR conditions of measurement can be altered and defined by the contextual limitations. Therefore, BMR is measured in the elusive "perfect" steady state, whereas RMR measurement is more accessible and thus, represents most, if not all measurements or estimates of daily energy expenditure. RMR measurements are recommended when estimating total daily energy expenditure (TEE) .

To measure RMR, you can use mathematical formulas, such as the Harris and Benedict Equation, which is one of the most common methods utilized today. You can access these formulas with calorie calculators on the Internet, an app, or through wearable devices. However, these methods measure RMR with varying degrees of accuracy.

To prepare for an RMR test, a subject should be fasting for 7 hours or greater, and mindful to avoid stimulants and stressors, such as caffeine, nicotine, and physical activities. The RMR test is a simple, non-invasive test that determines your RMR. The test also tells you your respiratory quotient (RQ), which shows you what percentage of your metabolism you burn in terms of carbohydrates vs. fat.

RMR is proportional to lean body mass and decreases approximately 0.01 kcal/min for each 1% increase in body fatness. Higher metabolic activity means your body burns more calories each day, and your BMR and RMR both tend to be higher if you’re physically fit. Your total daily energy expenditure (TDEE) is the total amount of calories you burn each day, consisting of calories burned through rest, exercise, and digestion.