body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
max-width: 800px;
margin: 0 auto;
padding: 20px;
}
.calculator-wrapper {
background: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.form-group {
margin-bottom: 20px;
}
.form-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #2c3e50;
}
.form-control {
width: 100%;
padding: 12px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.radio-group {
display: flex;
gap: 20px;
}
.radio-label {
font-weight: normal;
cursor: pointer;
display: flex;
align-items: center;
gap: 5px;
}
.btn-calculate {
background-color: #27ae60;
color: white;
border: none;
padding: 15px 30px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
width: 100%;
transition: background-color 0.2s;
}
.btn-calculate:hover {
background-color: #219150;
}
#bmr-result {
margin-top: 25px;
padding: 20px;
background-color: #fff;
border-left: 5px solid #27ae60;
display: none;
}
.result-value {
font-size: 32px;
font-weight: bold;
color: #27ae60;
}
.result-label {
font-size: 14px;
color: #666;
text-transform: uppercase;
letter-spacing: 1px;
}
.tdee-grid {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
gap: 15px;
margin-top: 20px;
border-top: 1px solid #eee;
padding-top: 20px;
}
.tdee-item {
background: #f1f8f4;
padding: 10px;
border-radius: 4px;
font-size: 14px;
}
.tdee-item strong {
display: block;
margin-bottom: 5px;
color: #2c3e50;
}
.content-section {
margin-top: 50px;
}
h2 {
color: #2c3e50;
border-bottom: 2px solid #27ae60;
padding-bottom: 10px;
margin-top: 30px;
}
h3 {
color: #34495e;
margin-top: 25px;
}
ul {
margin-bottom: 20px;
}
li {
margin-bottom: 10px;
}
.formula-box {
background: #eee;
padding: 15px;
border-radius: 4px;
font-family: monospace;
margin: 15px 0;
overflow-x: auto;
}
function calculateBMR() {
// Get input values
var age = parseFloat(document.getElementById('age').value);
var weight = parseFloat(document.getElementById('weight').value);
var height = parseFloat(document.getElementById('height').value);
var genderMale = document.getElementById('genderMale').checked;
var resultBox = document.getElementById('bmr-result');
// Validation
if (isNaN(age) || isNaN(weight) || isNaN(height) || age <= 0 || weight <= 0 || height <= 0) {
alert("Please enter valid positive numbers for Age, Weight, and Height.");
return;
}
// Mifflin-St Jeor Equation
// Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
// Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
var bmr = 0;
var baseCalculation = (10 * weight) + (6.25 * height) – (5 * age);
if (genderMale) {
bmr = baseCalculation + 5;
} else {
bmr = baseCalculation – 161;
}
// Round BMR to nearest whole number
bmr = Math.round(bmr);
// Display BMR
document.getElementById('bmrValue').innerText = bmr;
// Calculate TDEE (Total Daily Energy Expenditure)
// Sedentary: BMR * 1.2
// Lightly active: BMR * 1.375
// Moderately active: BMR * 1.55
// Very active: BMR * 1.725
document.getElementById('tdeeSedentary').innerText = Math.round(bmr * 1.2);
document.getElementById('tdeeLight').innerText = Math.round(bmr * 1.375);
document.getElementById('tdeeModerate').innerText = Math.round(bmr * 1.55);
document.getElementById('tdeeVery').innerText = Math.round(bmr * 1.725);
// Show result box
resultBox.style.display = 'block';
}
How Is Basal Metabolic Rate Calculated?
Understanding your Basal Metabolic Rate (BMR) is the foundation of any scientifically driven nutrition plan. Whether your goal is weight loss, muscle gain, or weight maintenance, calculating your BMR helps you determine the baseline number of calories your body requires just to exist.
What is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate is the number of calories your body burns while it is completely at rest. Imagine you stayed in bed all day without moving; your BMR is the energy required to keep your heart beating, your lungs breathing, your brain functioning, and your body temperature regulated. It accounts for approximately 60% to 75% of the total calories you burn every day.
The Calculation Methods
Over the years, scientists have developed several formulas to estimate BMR. The most commonly used and currently accepted as the most accurate standard is the Mifflin-St Jeor Equation.
1. The Mifflin-St Jeor Equation
Introduced in 1990, this formula is considered more accurate than its predecessors for modern lifestyles. The calculation differs slightly for men and women due to differences in lean body mass.
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
2. The Harris-Benedict Equation
Original revised in 1984, this was the standard for many years. While still widely used, it tends to over-estimate BMR slightly in individuals with a higher body fat percentage.
Example Calculation
Let's look at how the calculation works for a specific example using the Mifflin-St Jeor equation:
- Profile: A 35-year-old female
- Weight: 68 kg
- Height: 165 cm
Step 1: Calculate weight component: 10 × 68 = 680
Step 2: Calculate height component: 6.25 × 165 = 1,031.25
Step 3: Calculate age component: 5 × 35 = 175
Step 4: Apply the formula:
(680 + 1,031.25 – 175) – 161 = 1,375.25
This individual has a BMR of approximately 1,375 calories per day.
Factors Influencing BMR
While the formulas provide a solid estimate, your actual metabolic rate is influenced by several biological factors:
- Muscle Mass: Muscle tissue burns more calories at rest than fat tissue. Individuals with higher muscle mass have a higher BMR.
- Age: Metabolism naturally slows down as you age, largely due to a loss of muscle mass and hormonal changes.
- Gender: Men typically have less body fat and more muscle mass than women of the same age and weight, resulting in a higher BMR.
- Genetics: Your genetic makeup plays a significant role in your baseline metabolic speed.
From BMR to TDEE
Calculating BMR is just the first step. To determine how many calories you need to eat to maintain your current weight, you must calculate your Total Daily Energy Expenditure (TDEE). This is done by multiplying your BMR by an activity factor ranging from 1.2 (sedentary) to 1.9 (extremely active).