Metabolism Rate Calculator (BMR – Mifflin-St Jeor)
Male
Female
How to Calculate Metabolism Rate
This calculator helps you estimate your Basal Metabolic Rate (BMR), which is the number of calories your body needs to perform basic life-sustaining functions at rest. Understanding your BMR is a crucial first step in managing your weight, whether your goal is to lose, gain, or maintain it. Your BMR accounts for a significant portion of your daily calorie expenditure, with physical activity being the other major factor.
Several factors influence your BMR, including your age, sex, weight, and height. Genetics also play a role, but these are the primary metrics used in common BMR formulas like the Harris-Benedict or Mifflin-St Jeor equations.
**Mifflin-St Jeor Equation (considered more accurate for most people):**
* **For Men:** BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
* **For Women:** BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
**Harris-Benedict Equation (Original):**
* **For Men:** BMR = 66.5 + (13.75 × weight in kg) + (5.003 × height in cm) – (6.755 × age in years)
* **For Women:** BMR = 655.1 + (9.563 × weight in kg) + (1.850 × height in cm) – (4.676 × age in years)
This calculator uses the Mifflin-St Jeor equation. Once you have your BMR, you can then estimate your Total Daily Energy Expenditure (TDEE) by multiplying your BMR by an activity factor.
function calculateBMR() {
var gender = document.getElementById("gender").value;
var weightKg = parseFloat(document.getElementById("weightKg").value);
var heightCm = parseFloat(document.getElementById("heightCm").value);
var ageYears = parseFloat(document.getElementById("ageYears").value);
var bmr = 0;
if (isNaN(weightKg) || isNaN(heightCm) || isNaN(ageYears) || weightKg <= 0 || heightCm <= 0 || ageYears <= 0) {
document.getElementById("result").innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
if (gender === "male") {
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * ageYears) + 5;
} else { // female
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * ageYears) – 161;
}
document.getElementById("result").innerHTML = "Your estimated Basal Metabolic Rate (BMR) is: " + bmr.toFixed(2) + " calories per day.";
}
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