Sedentary (little or no exercise)
Lightly active (exercise 1-3 days/week)
Moderately active (exercise 3-5 days/week)
Active (exercise 6-7 days/week)
Very active (hard exercise 2x/day)
Your Results
Basal Metabolic Rate (BMR)
0
calories / day
Maintenance (TDEE)
0
calories / day
Daily Calorie Goals:
Weight Loss (0.5kg/week):–
Muscle Gain (Mild Surplus):–
function calculateBMR() {
var gender = document.getElementById('gender').value;
var age = parseFloat(document.getElementById('age').value);
var weight = parseFloat(document.getElementById('weight').value);
var height = parseFloat(document.getElementById('height').value);
var activity = parseFloat(document.getElementById('activity').value);
var resultArea = document.getElementById('result-area');
if (isNaN(age) || isNaN(weight) || isNaN(height)) {
alert("Please fill in all fields with valid numbers.");
return;
}
var bmr = 0;
// Mifflin-St Jeor Equation
if (gender === 'male') {
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else {
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
var tdee = bmr * activity;
var loss = tdee – 500;
var gain = tdee + 300;
document.getElementById('bmr-value').innerText = Math.round(bmr).toLocaleString();
document.getElementById('tdee-value').innerText = Math.round(tdee).toLocaleString();
document.getElementById('loss-val').innerText = Math.round(loss).toLocaleString() + " kcal";
document.getElementById('gain-val').innerText = Math.round(gain).toLocaleString() + " kcal";
resultArea.style.display = 'block';
resultArea.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}
Understanding Your Basal Metabolic Rate (BMR)
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at rest to maintain vital functions, such as breathing, blood circulation, and cell production. Essentially, it is the energy you would expend if you stayed in bed all day doing nothing.
The Mifflin-St Jeor Equation
This calculator uses the Mifflin-St Jeor Equation, widely considered the most accurate formula for estimating metabolic rate in modern populations. The formulas are as follows:
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
From BMR to TDEE
Your BMR is only the baseline. To understand how many calories you actually burn in a day, we multiply your BMR by an activity factor to find your Total Daily Energy Expenditure (TDEE). This accounts for your movements, workouts, and daily chores.
Practical Examples
Knowing these numbers is critical for weight management:
For Weight Loss: You must create a calorie deficit. Consuming 500 calories less than your TDEE typically leads to a loss of about 0.5kg (1 lb) per week.
For Muscle Gain: You need a calorie surplus. Consuming 200–500 calories above your TDEE provides the energy your body needs to build new muscle tissue.
For Maintenance: Consuming exactly your TDEE will keep your weight stable.
SEO Tip: Metabolic rate is influenced by lean muscle mass. Increasing your muscle percentage through strength training can effectively raise your BMR, allowing you to burn more calories even while sleeping.