Basal Metabolic Rate (BMR) Calculator
What is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate (BMR) is the minimum amount of energy (calories) your body needs to perform essential life-sustaining functions while at rest. These functions include breathing, circulating blood, maintaining body temperature, cell production, and brain activity. Essentially, it's the energy your body burns just to keep you alive and functioning at a resting state, before you even consider physical activity.
Understanding your BMR is a crucial first step in managing your weight and overall health. It helps you determine a baseline calorie intake necessary to maintain your current weight. If you aim to lose weight, you'll need to consume fewer calories than your total daily energy expenditure (which includes BMR plus activity). If you aim to gain weight, you'll need to consume more.
How is BMR Calculated?
The most commonly used formulas for calculating BMR are the Harris-Benedict Equation (revised) and the Mifflin-St Jeor Equation. The Mifflin-St Jeor equation is generally considered more accurate for most people.
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
This calculator uses the Mifflin-St Jeor equation to provide an estimate of your Basal Metabolic Rate.
Example Calculation:
Let's consider a 30-year-old female who weighs 60 kg and is 165 cm tall.
- Weight = 60 kg
- Height = 165 cm
- Age = 30 years
- Gender = Female
Using the Mifflin-St Jeor equation for women:
BMR = (10 × 60) + (6.25 × 165) – (5 × 30) – 161
BMR = 600 + 1031.25 – 150 – 161
BMR = 1320.25 calories per day
This means her body needs approximately 1320.25 calories per day to maintain basic functions at rest. Her total daily energy expenditure would be higher depending on her activity level.
function calculateBMR() {
var gender = document.getElementById("gender").value;
var weight = parseFloat(document.getElementById("weight").value);
var height = parseFloat(document.getElementById("height").value);
var age = parseFloat(document.getElementById("age").value);
var resultDiv = document.getElementById("result");
var bmr = 0;
if (isNaN(weight) || isNaN(height) || isNaN(age) || weight <= 0 || height <= 0 || age <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for weight, height, and age.";
return;
}
if (gender === "male") {
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else { // female
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
resultDiv.innerHTML = "Your estimated Basal Metabolic Rate (BMR) is:
" + bmr.toFixed(2) + " calories/day";
}
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