Calculate Your Resting Energy Expenditure Based on Height and Weight
BMR Calculator
Enter your weight in kilograms (kg).
Enter your height in centimeters (cm).
Your BMR Results
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(kcal/day)
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Mifflin-St Jeor Equation (Simplified for height/weight only)
The Mifflin-St Jeor equation is a widely accepted formula for estimating BMR. For simplicity in this calculator, we use a version that primarily relies on weight and height.
BMR vs. Weight for Constant Height
BMR Estimates at Different Weights (Constant Height)
Weight (kg)
Estimated BMR (kcal/day)
What is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to perform essential life-sustaining functions while at rest. Think of it as the energy your body expends to keep your heart beating, lungs breathing, brain functioning, and cells repairing, all in a state of complete physical and mental rest, typically measured after an overnight fast. Understanding your BMR is a fundamental step in managing your weight and optimizing your overall health. It represents the baseline energy expenditure before any physical activity is considered.
Who Should Use a BMR Calculator?
Anyone interested in weight management, fitness, or understanding their body's energy needs can benefit from calculating their BMR. This includes individuals looking to lose weight, gain muscle, maintain their current weight, or simply gain a better insight into their metabolism. Athletes, nutritionists, and healthcare professionals also use BMR as a foundational metric.
Common Misconceptions about BMR:
A frequent misconception is that BMR is the total number of calories you burn in a day. This is incorrect; BMR is only the resting component. Total daily energy expenditure (TDEE) includes BMR plus the calories burned through physical activity, the thermic effect of food, and other non-resting activities. Another myth is that BMR is fixed; while it's relatively stable, it can be influenced by factors like muscle mass, age, and hormonal changes. This calculator focuses on the core BMR calculation based on physical metrics.
BMR Formula and Mathematical Explanation
The most commonly used and scientifically validated formula for estimating BMR is the Mifflin-St Jeor equation. While it traditionally includes age and sex, a simplified version focusing solely on height and weight can provide a useful estimate, especially when those are the primary available metrics. This calculator utilizes a simplified approach derived from the principles of the Mifflin-St Jeor equation, emphasizing the direct relationship between body mass, height, and resting energy expenditure.
The core idea is that larger bodies require more energy to maintain basic functions. Height plays a role as it influences overall body size and surface area, which are correlated with metabolic rate.
Simplified Formula Concept:
While the exact Mifflin-St Jeor equation requires sex and age, the underlying principle is that metabolic rate scales with body size. For this calculator, we'll use a conceptual representation that highlights the impact of weight and height. A common simplified approach often relates BMR proportionally to weight and height, acknowledging that more mass and greater stature generally correlate with higher energy needs at rest.
For the purpose of this calculator, we will use the following simplified calculation logic that captures the essence of how height and weight influence BMR:
Calculation Logic:
BMR = (Weight in kg * Constant_W) + (Height in cm * Constant_H) + Base_Value
Where:
Constant_W = A factor representing the metabolic contribution of body mass.
Constant_H = A factor representing the metabolic contribution of body height.
Base_Value = A baseline energy requirement.
*Note: The specific constants (Constant_W, Constant_H, Base_Value) are derived from statistical analysis of metabolic data and are adjusted to provide a reasonable estimate. For this calculator, we'll use values that reflect general trends:
Constant_W ≈ 10
Constant_H ≈ 6.25
Base_Value ≈ -5 (This is a simplification; the actual Mifflin-St Jeor equation uses sex-specific base values and age.)
This simplified formula aims to demonstrate the relationship rather than provide a clinically precise BMR without age and sex.
Variables Table
Variable
Meaning
Unit
Typical Range (for this calculator)
Weight
Body mass
Kilograms (kg)
1 – 500 kg
Height
Body stature
Centimeters (cm)
25 – 250 cm
BMR
Basal Metabolic Rate
Kilocalories per day (kcal/day)
Calculated value, typically 1000 – 3000+ kcal/day
Practical Examples (Real-World Use Cases)
Understanding BMR through practical examples helps illustrate its significance in daily life and health planning.
Example 1: Weight Management Goal
Scenario: Sarah is a 30-year-old woman (though age/sex aren't used in this simplified calculator) who wants to lose weight. She weighs 75 kg and is 165 cm tall. She wants to know her baseline calorie needs.
Interpretation: Sarah's body needs approximately 1776 kcal per day just to maintain basic functions at rest. To lose weight, she would need to consume fewer calories than her Total Daily Energy Expenditure (TDEE), which includes this BMR plus calories burned from activity. A deficit of 500 kcal per day typically leads to about 1 pound of weight loss per week.
Example 2: Athlete's Baseline Energy
Scenario: Mark is a male athlete (age/sex not used) focusing on muscle gain. He weighs 90 kg and is 185 cm tall. He needs to ensure he's consuming enough calories to support his training and recovery.
Interpretation: Mark's resting metabolism requires about 2051 kcal daily. As an athlete, his TDEE will be significantly higher due to intense training. To gain muscle, he needs to consume calories above his TDEE (a caloric surplus). Understanding his BMR helps him set a foundation for calculating his total caloric intake.
How to Use This BMR Calculator
Using this Basal Metabolic Rate (BMR) calculator is straightforward. Follow these steps to get your estimated resting energy expenditure:
Enter Your Weight: Input your current body weight in kilograms (kg) into the "Weight" field. Ensure accuracy for the best estimate.
Enter Your Height: Input your height in centimeters (cm) into the "Height" field. Double-check that you are using centimeters, not meters or feet/inches.
Calculate: Click the "Calculate BMR" button. The calculator will process your inputs using the simplified Mifflin-St Jeor-based formula.
View Results: Your estimated BMR will be displayed prominently in kilocalories per day (kcal/day). You will also see the input values you used and the formula type. Intermediate values like weight and height used in the calculation are also shown for clarity.
Analyze the Chart and Table: Explore the dynamic chart and table which illustrate how BMR can change with weight, keeping height constant. This provides a visual understanding of the relationship.
Reset or Copy: Use the "Reset" button to clear the fields and start over with new measurements. The "Copy Results" button allows you to easily save or share your calculated BMR and related data.
How to Read Results: The primary result is your BMR in kcal/day. This number represents the calories your body burns at complete rest. It's a foundational number; your total daily calorie needs (TDEE) will be higher depending on your activity level.
Decision-Making Guidance:
Weight Loss: Consume fewer calories than your TDEE. Your BMR helps estimate your TDEE.
Weight Gain: Consume more calories than your TDEE.
Maintenance: Consume calories roughly equal to your TDEE.
Remember that BMR is an estimate. Factors like muscle mass, genetics, and hormones can influence your actual metabolic rate. For precise nutritional planning, consult with a healthcare professional or registered dietitian. This tool provides a valuable starting point for understanding your energy needs.
Key Factors That Affect BMR Results
While this calculator uses a simplified model based on height and weight, several other factors significantly influence an individual's actual Basal Metabolic Rate (BMR). Understanding these can provide a more complete picture of your energy needs.
Body Composition (Muscle Mass): Muscle tissue is metabolically more active than fat tissue. Individuals with higher muscle mass generally have a higher BMR, even at the same weight and height. This is a critical factor often not captured by simple height/weight calculators.
Age: Metabolic rate tends to decrease with age, typically starting after age 20-30. This is partly due to a natural decline in muscle mass and hormonal changes.
Sex: On average, males tend to have a higher BMR than females, primarily due to differences in body composition (higher muscle mass) and body size. Standard BMR formulas account for this.
Genetics: Individual genetic makeup plays a role in determining metabolic rate. Some people naturally have a faster metabolism than others.
Hormonal Factors: Thyroid hormones, in particular, play a crucial role in regulating metabolism. Conditions like hyperthyroidism (overactive thyroid) can significantly increase BMR, while hypothyroidism (underactive thyroid) can decrease it.
Environmental Temperature: In very cold or very hot environments, your body expends extra energy to maintain its core temperature, potentially increasing BMR.
Dietary Intake & Fasting: Prolonged severe calorie restriction or fasting can lower BMR as the body attempts to conserve energy. Conversely, the thermic effect of food (TEF) – the energy used to digest, absorb, and metabolize food – temporarily increases metabolic rate after meals.
Health Status: Illness, injury, or fever can increase BMR as the body works harder to heal and fight infection.
While this calculator provides a baseline estimate using height and weight, incorporating these additional factors offers a more nuanced understanding of individual metabolic needs. For precise calculations, especially in clinical settings, more comprehensive formulas and assessments are recommended.
Frequently Asked Questions (FAQ)
Q1: What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest. TDEE (Total Daily Energy Expenditure) is the total calories you burn in a day, including BMR plus calories burned from all physical activities, digestion (thermic effect of food), and other bodily functions. TDEE is always higher than BMR.
Q2: Is the Mifflin-St Jeor equation the only way to calculate BMR?
No, there are other formulas like the Harris-Benedict equation (original and revised). However, Mifflin-St Jeor is generally considered more accurate for most people in modern populations. This calculator uses a simplified version focusing on height and weight.
Q3: Can my BMR change over time?
Yes, your BMR can change. Factors like significant weight loss or gain, changes in muscle mass, aging, and certain medical conditions can affect your metabolic rate.
Q4: Does muscle mass really affect BMR?
Absolutely. Muscle tissue is more metabolically active than fat tissue, meaning it burns more calories even at rest. Increasing muscle mass can lead to a higher BMR.
Q5: How accurate is a BMR calculator?
BMR calculators provide an estimate. The accuracy depends on the formula used and individual variations. Factors like genetics, hormones, and precise body composition aren't always accounted for in simple calculators. They are best used as a starting point.
Q6: Should I eat exactly my BMR calories?
No, eating only your BMR calories is generally not recommended unless under strict medical supervision for specific conditions. Your body needs more calories than just its resting requirement to function throughout the day and support activity. Aiming for a calorie intake based on your TDEE is more appropriate for weight management.
Q7: What if my weight or height is outside the typical range?
This calculator uses standard ranges for inputs. If your measurements are significantly outside these ranges (e.g., extreme obesity or dwarfism), the estimate may be less reliable. Consult a healthcare professional for personalized assessments.
Q8: How can I increase my BMR?
The most effective way to increase your BMR is by increasing your muscle mass through strength training exercises. Maintaining a healthy diet and avoiding prolonged severe calorie restriction can also help prevent a decrease in BMR.
Related Tools and Internal Resources
BMI CalculatorCalculate your Body Mass Index (BMI) to assess your weight category relative to your height.
Calorie Needs CalculatorEstimate your Total Daily Energy Expenditure (TDEE) based on BMR and activity level.
Macronutrient CalculatorDetermine the ideal balance of protein, carbohydrates, and fats for your diet.
Water Intake CalculatorCalculate your recommended daily water consumption for optimal hydration.
var weightInput = document.getElementById('weight');
var heightInput = document.getElementById('height');
var weightError = document.getElementById('weightError');
var heightError = document.getElementById('heightError');
var bmrResultDiv = document.getElementById('bmrResult');
var resultWeightDiv = document.getElementById('resultWeight');
var resultHeightDiv = document.getElementById('resultHeight');
var bmrChartCanvas = document.getElementById('bmrChart');
var bmrTableBody = document.querySelector('#bmrTable tbody');
var chartInstance = null; // To hold the chart instance
// Default values for reset
var defaultWeight = 70;
var defaultHeight = 175;
function validateInput(value, min, max, errorElement, inputName) {
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if (numValue max) {
errorElement.textContent = inputName + ' must be between ' + min + ' and ' + max + '.';
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errorElement.textContent = "; // Clear error
return true;
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function calculateBMR() {
var weight = weightInput.value;
var height = heightInput.value;
var isValidWeight = validateInput(weight, 1, 500, weightError, 'Weight');
var isValidHeight = validateInput(height, 25, 250, heightError, 'Height');
if (!isValidWeight || !isValidHeight) {
// Clear results if validation fails
bmrResultDiv.textContent = '–';
resultWeightDiv.textContent = '–';
resultHeightDiv.textContent = '–';
if (chartInstance) {
chartInstance.destroy(); // Destroy previous chart if exists
chartInstance = null;
}
clearTable();
return;
}
var w = parseFloat(weight);
var h = parseFloat(height);
// Simplified Mifflin-St Jeor based calculation
// BMR = (Weight in kg * 10) + (Height in cm * 6.25) – 5 (simplified base)
var bmr = (w * 10) + (h * 6.25) – 5;
bmrResultDiv.textContent = bmr.toFixed(2);
resultWeightDiv.textContent = w.toFixed(2) + ' kg';
resultHeightDiv.textContent = h.toFixed(2) + ' cm';
updateChartAndTable(h); // Update chart and table with current height
}
function updateChartAndTable(currentHeight) {
var weightData = [];
var bmrData = [];
var tableRows = ";
// Generate data for chart and table for a range of weights
for (var w = 40; w <= 120; w += 5) {
var tempBmr = (w * 10) + (currentHeight * 6.25) – 5;
weightData.push(w);
bmrData.push(tempBmr);
tableRows += '
' + w.toFixed(0) + ' kg
' + tempBmr.toFixed(2) + ' kcal/day
';
}
// Update table
bmrTableBody.innerHTML = tableRows;
// Update chart
var ctx = bmrChartCanvas.getContext('2d');
if (chartInstance) {
chartInstance.destroy(); // Destroy previous chart instance
}
chartInstance = new Chart(ctx, {
type: 'line',
data: {
labels: weightData.map(function(w) { return w + ' kg'; }),
datasets: [{
label: 'Estimated BMR (kcal/day)',
data: bmrData,
borderColor: 'var(–primary-color)',
backgroundColor: 'rgba(0, 74, 153, 0.1)',
fill: true,
tension: 0.1
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options: {
responsive: true,
maintainAspectRatio: false,
scales: {
y: {
beginAtZero: true,
title: {
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text: 'BMR (kcal/day)'
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title: {
display: true,
text: 'Weight (kg)'
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plugins: {
legend: {
display: true,
position: 'top',
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title: {
display: true,
text: 'BMR vs. Weight for Height: ' + currentHeight.toFixed(0) + ' cm'
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function clearTable() {
bmrTableBody.innerHTML = ";
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function resetCalculator() {
weightInput.value = defaultWeight;
heightInput.value = defaultHeight;
weightError.textContent = ";
heightError.textContent = ";
bmrResultDiv.textContent = '–';
resultWeightDiv.textContent = '–';
resultHeightDiv.textContent = '–';
if (chartInstance) {
chartInstance.destroy();
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clearTable();
// Optionally, re-calculate with default values
// calculateBMR();
}
function copyResults() {
var bmrValue = bmrResultDiv.textContent;
var weightValue = resultWeightDiv.textContent;
var heightValue = resultHeightDiv.textContent;
var formula = "Simplified Mifflin-St Jeor (Height & Weight only)";
if (bmrValue === '–') {
alert("No results to copy yet. Please calculate first.");
return;
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var textToCopy = "— BMR Calculation Results —\n\n" +
"Basal Metabolic Rate (BMR): " + bmrValue + "\n" +
"Weight Used: " + weightValue + "\n" +
"Height Used: " + heightValue + "\n" +
"Formula: " + formula + "\n\n" +
"Note: This is an estimate based on height and weight only.";
navigator.clipboard.writeText(textToCopy).then(function() {
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console.error('Failed to copy text: ', err);
alert('Failed to copy results. Please try manually.');
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// Initial setup for chart and table on load
document.addEventListener('DOMContentLoaded', function() {
// Set default values
weightInput.value = defaultWeight;
heightInput.value = defaultHeight;
// Calculate initial results based on defaults
calculateBMR();
});
// Add Chart.js library dynamically if not present
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var script = document.createElement('script');
script.src = 'https://cdn.jsdelivr.net/npm/chart.js@3.7.0/dist/chart.min.js';
script.onload = function() {
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// Ensure default values are set and calculation runs
weightInput.value = defaultWeight;
heightInput.value = defaultHeight;
calculateBMR();
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document.head.appendChild(script);
} else {
// If Chart.js is already loaded, just run the initial calculation
weightInput.value = defaultWeight;
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calculateBMR();
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