Understanding Your Basal Metabolic Rate (BMR)
Your Basal Metabolic Rate (BMR) is the minimum amount of energy, in the form of calories, your body needs to maintain vital functions such as breathing, circulation, cell production, and hormone regulation. This rate is influenced by several factors, including age, gender, weight, and height. The BMR is the energy expenditure when you are in a completely resting state, both physically and mentally.
The most commonly used formulas for calculating BMR are the Harris-Benedict equation and the Mifflin-St Jeor equation. The Mifflin-St Jeor equation is generally considered more accurate for the general population and is the one used in this calculator.
Mifflin-St Jeor Equation:
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
Knowing your BMR is the first step in understanding your total daily energy expenditure. Your Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor that accounts for your exercise and daily movements. This calculator focuses solely on the BMR component.
function calculateBMR() {
var weight = document.getElementById("weight").value;
var height = document.getElementById("height").value;
var age = document.getElementById("age").value;
var gender = document.getElementById("gender").value;
var resultDiv = document.getElementById("result");
// Clear previous results
resultDiv.innerHTML = "";
// Validate inputs
if (weight === "" || height === "" || age === "") {
resultDiv.innerHTML = "Please fill in all fields.";
return;
}
var weightNum = parseFloat(weight);
var heightNum = parseFloat(height);
var ageNum = parseFloat(age);
if (isNaN(weightNum) || isNaN(heightNum) || isNaN(ageNum) || weightNum <= 0 || heightNum <= 0 || ageNum <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for weight, height, and age.";
return;
}
var bmr;
if (gender === "male") {
bmr = (10 * weightNum) + (6.25 * heightNum) – (5 * ageNum) + 5;
} else { // female
bmr = (10 * weightNum) + (6.25 * heightNum) – (5 * ageNum) – 161;
}
resultDiv.innerHTML = "Your estimated Basal Metabolic Rate (BMR) is:
" + bmr.toFixed(2) + " calories per day.";
}
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