How to Calculate the Resting Metabolic Rate

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RMR Calculator

Male Female

Resting Metabolic Rate (RMR) is the total number of calories your body burns while at rest. Even when you are sitting on the couch or sleeping, your body requires energy to maintain vital functions such as breathing, blood circulation, organ function, and neurological processing.

RMR vs. BMR: What is the Difference?

While often used interchangeably, Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) differ slightly in how they are measured. BMR is measured under very restrictive clinical conditions (e.g., after an overnight fast and 8 hours of sleep in a darkened room). RMR is a more realistic measurement for daily life, as it is taken under less restrictive conditions and accounts for the energy used for low-effort daily activities and digestion.

The Mifflin-St Jeor Equation

This calculator utilizes the Mifflin-St Jeor Equation, which is currently considered the most accurate formula for predicting RMR in healthy adults. The formula is split by biological sex because muscle mass and hormonal profiles generally lead to different metabolic baselines.

• For Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
• For Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161

Practical Example:
Imagine a 35-year-old male who weighs 85 kg and is 180 cm tall.
Calculation: (10 × 85) + (6.25 × 180) – (5 × 35) + 5
Calculation: 850 + 1125 – 175 + 5 = 1,805 Calories/day.
This individual requires 1,805 calories daily just to sustain basic life functions without any additional movement.

Factors That Influence Your Metabolic Rate

Several factors can cause your RMR to be higher or lower than the average calculated by the formula:

• Muscle Mass: Muscle tissue is more metabolically active than fat tissue. The more muscle you have, the higher your RMR.
• Age: Metabolic rate typically slows down as we age, largely due to a natural loss of muscle mass.
• Genetics: Some individuals naturally have a "faster" or "slower" metabolism due to genetic factors.
• Climate: Keeping the body at a core temperature in very cold or very hot environments requires extra energy.
• Health Status: Fever, illness, or certain hormonal conditions (like thyroid disorders) can significantly shift your RMR.

How to Use This Information

Knowing your RMR is the first step in creating a sustainable nutrition plan. To find your "Maintenance Calories" (the total amount you burn in a day), you must multiply your RMR by an activity factor (usually between 1.2 for sedentary individuals to 1.9 for elite athletes). From there, you can subtract calories for weight loss or add them for muscle gain.

function calculateRMR() { var gender = document.getElementById("rmrGender").value; var weight = parseFloat(document.getElementById("rmrWeight").value); var height = parseFloat(document.getElementById("rmrHeight").value); var age = parseFloat(document.getElementById("rmrAge").value); var resultBox = document.getElementById("rmrResultBox"); var resultValue = document.getElementById("rmrValue"); if (isNaN(weight) || isNaN(height) || isNaN(age) || weight <= 0 || height <= 0 || age <= 0) { alert("Please enter valid positive numbers for weight, height, and age."); return; } var rmr = 0; if (gender === "male") { // Mifflin-St Jeor for Men rmr = (10 * weight) + (6.25 * height) – (5 * age) + 5; } else { // Mifflin-St Jeor for Women rmr = (10 * weight) + (6.25 * height) – (5 * age) – 161; } resultValue.innerText = Math.round(rmr).toLocaleString(); resultBox.style.display = "block"; }