RMR Calculator

What Is Resting Metabolic Rate (RMR)?

Resting Metabolic Rate (RMR) represents the number of calories your body burns while at complete rest to maintain vital involuntary physiological functions. These baseline processes include breathing, circulating blood, cellular repair, maintaining body temperature, protein synthesis, and brain activity. RMR typically accounts for 60% to 75% of your total daily energy expenditure (TDEE).

RMR vs. BMR: Understanding the Difference

While Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) are closely related and often used interchangeably, they differ in measurement conditions:

• BMR (Basal Metabolic Rate): Measured in strict clinical laboratory conditions after an overnight fast (12 hours) and immediately upon waking in a thermo-neutral room without any physical movement. You can also explore our BMR Calculator.
• RMR (Resting Metabolic Rate): Measured under less restrictive resting conditions without requiring an overnight clinic stay. It is generally 3% to 10% higher than BMR due to recent digestion, minor movement, or ambient temperature variations.

RMR Calculation Formulas

This calculator employs the four most accurate and widely validated clinical equations:

1. Mifflin-St Jeor Equation (Clinical Standard)

Widely considered the most accurate formula for modern populations without body composition data:

• Men: $$\text{RMR} = 10 \times \text{weight (kg)} + 6.25 \times \text{height (cm)} - 5 \times \text{age (years)} + 5$$
• Women: $$\text{RMR} = 10 \times \text{weight (kg)} + 6.25 \times \text{height (cm)} - 5 \times \text{age (years)} - 161$$

2. Revised Harris-Benedict Equation (Roza & Shizgal, 1984)

• Men: $$\text{RMR} = 88.362 + (13.397 \times \text{weight in kg}) + (4.799 \times \text{height in cm}) - (5.677 \times \text{age in years})$$
• Women: $$\text{RMR} = 447.593 + (9.247 \times \text{weight in kg}) + (3.098 \times \text{height in cm}) - (4.330 \times \text{age in years})$$

3. Katch-McArdle & Cunningham Equations (Lean Mass Based)

When body fat percentage is known, formulas based on Lean Body Mass (LBM) provide superior accuracy for athletes and muscular individuals:

• Katch-McArdle: $$\text{RMR} = 370 + 21.6 \times \text{LBM (kg)}$$
• Cunningham: $$\text{RMR} = 500 + 22 \times \text{LBM (kg)}$$

How to Use RMR for Weight Loss, Maintenance, and Muscle Gain

To determine how many calories you should consume per day, multiply your RMR by your physical activity level factor to find your Total Daily Energy Expenditure (TDEE). Check our Calorie Deficit Calculator to plan precise target deficits.

• Weight Loss: Consume 300 to 500 kcal below your TDEE while keeping intake safely above your RMR.
• Maintenance: Consume calories equal to your estimated TDEE.
• Muscle Gain: Consume a mild surplus of 250 to 400 kcal above your TDEE with adequate protein.