.rmr-calculator-container {
max-width: 600px;
margin: 0 auto;
padding: 25px;
background-color: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
font-family: Arial, sans-serif;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.rmr-calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 20px;
}
.form-group {
margin-bottom: 15px;
}
.form-group label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.radio-group {
display: flex;
gap: 15px;
margin-bottom: 10px;
}
.radio-group label {
font-weight: normal;
cursor: pointer;
}
.form-control {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
font-size: 16px;
}
.imperial-height-group {
display: flex;
gap: 10px;
}
.btn-calculate {
display: block;
width: 100%;
padding: 12px;
background-color: #2c7a7b;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background 0.3s;
}
.btn-calculate:hover {
background-color: #235c5d;
}
#rmr-result {
margin-top: 20px;
padding: 15px;
background-color: #e6fffa;
border: 1px solid #b2f5ea;
border-radius: 4px;
text-align: center;
display: none;
}
.result-value {
font-size: 32px;
font-weight: bold;
color: #2c7a7b;
}
.result-label {
font-size: 14px;
color: #666;
margin-top: 5px;
}
.unit-toggle {
text-align: center;
margin-bottom: 20px;
padding-bottom: 15px;
border-bottom: 1px solid #eee;
}
.content-section {
max-width: 800px;
margin: 40px auto;
font-family: Arial, sans-serif;
line-height: 1.6;
color: #333;
}
.content-section h2 {
color: #2c7a7b;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
margin-top: 30px;
}
.content-section ul {
margin-left: 20px;
}
function toggleUnits() {
var radios = document.getElementsByName('units');
var selectedUnit = 'metric';
for (var i = 0; i < radios.length; i++) {
if (radios[i].checked) {
selectedUnit = radios[i].value;
}
}
var metricDiv = document.getElementById('metric-inputs');
var imperialDiv = document.getElementById('imperial-inputs');
if (selectedUnit === 'metric') {
metricDiv.style.display = 'block';
imperialDiv.style.display = 'none';
} else {
metricDiv.style.display = 'none';
imperialDiv.style.display = 'block';
}
// Hide result when switching units to avoid confusion
document.getElementById('rmr-result').style.display = 'none';
}
function calculateRMR() {
// 1. Get Common Inputs
var age = parseFloat(document.getElementById('age').value);
var genderRadios = document.getElementsByName('gender');
var gender = 'male';
for (var i = 0; i < genderRadios.length; i++) {
if (genderRadios[i].checked) {
gender = genderRadios[i].value;
}
}
var unitRadios = document.getElementsByName('units');
var unit = 'metric';
for (var i = 0; i < unitRadios.length; i++) {
if (unitRadios[i].checked) {
unit = unitRadios[i].value;
}
}
// 2. Validate Age
if (isNaN(age) || age <= 0) {
alert("Please enter a valid age.");
return;
}
var weightKg = 0;
var heightCm = 0;
// 3. Get and Convert Inputs based on Unit System
if (unit === 'metric') {
var w = parseFloat(document.getElementById('weight-kg').value);
var h = parseFloat(document.getElementById('height-cm').value);
if (isNaN(w) || w <= 0) { alert("Please enter a valid weight in kg."); return; }
if (isNaN(h) || h <= 0) { alert("Please enter a valid height in cm."); return; }
weightKg = w;
heightCm = h;
} else {
var wLbs = parseFloat(document.getElementById('weight-lbs').value);
var hFt = parseFloat(document.getElementById('height-ft').value);
var hIn = parseFloat(document.getElementById('height-in').value);
if (isNaN(wLbs) || wLbs <= 0) { alert("Please enter a valid weight in lbs."); return; }
if (isNaN(hFt)) hFt = 0;
if (isNaN(hIn)) hIn = 0;
if (hFt === 0 && hIn === 0) { alert("Please enter a valid height."); return; }
// Conversions
// 1 lb = 0.453592 kg
weightKg = wLbs * 0.453592;
// 1 ft = 30.48 cm, 1 in = 2.54 cm
heightCm = (hFt * 30.48) + (hIn * 2.54);
}
// 4. Calculate RMR using 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 rmr = 0;
var partWeight = 10 * weightKg;
var partHeight = 6.25 * heightCm;
var partAge = 5 * age;
if (gender === 'male') {
rmr = partWeight + partHeight – partAge + 5;
} else {
rmr = partWeight + partHeight – partAge – 161;
}
// 5. Display Result
rmr = Math.round(rmr);
var resultDiv = document.getElementById('rmr-result');
var resultVal = document.getElementById('result-calories');
resultVal.innerText = rmr;
resultDiv.style.display = 'block';
}
How to Calculate Resting Metabolism Rate (RMR)
Understanding your body's energy needs is the fundamental first step in any fitness, weight loss, or health journey. Your Resting Metabolic Rate (RMR) represents the number of calories your body burns while at complete rest to maintain basic physiological functions like breathing, circulating blood, and cellular reproduction. This calculator uses the Mifflin-St Jeor equation, widely considered the most accurate formula for estimating RMR in the general population.
What is Resting Metabolic Rate (RMR)?
RMR measures the energy required to keep your body functioning if you were to lie in bed all day doing absolutely nothing. It accounts for approximately 60% to 75% of your total daily energy expenditure (TDEE).
While often used interchangeably with Basal Metabolic Rate (BMR), there is a slight difference:
- BMR (Basal Metabolic Rate): Measured under very strict laboratory conditions (fasting, dark room, immediately upon waking).
- RMR (Resting Metabolic Rate): Measured under less strict conditions and is generally more practical for real-world estimates. RMR is usually slightly higher than BMR due to the thermic effect of food and small movements.
The Formula: Mifflin-St Jeor Equation
This calculator utilizes the Mifflin-St Jeor equation, which was introduced in 1990 and has been validated by numerous studies as more accurate than the older Harris-Benedict equation. The math varies slightly depending on gender:
For Men:
RMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
For Women:
RMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161
Example Calculation
Let's calculate the RMR for a 35-year-old woman who weighs 68 kg (150 lbs) and is 165 cm (5'5″) tall.
- Weight: 10 × 68 = 680
- Height: 6.25 × 165 = 1,031.25
- Age: 5 × 35 = 175
- Combine: 680 + 1,031.25 – 175 – 161 = 1,375.25 Calories/day
This means her body requires approximately 1,375 calories just to exist. To lose weight, she would typically eat slightly above this number but below her Total Daily Energy Expenditure.
Factors That Influence Your RMR
While the formula provides a solid baseline, several factors can cause your actual metabolic rate to vary:
- Muscle Mass: Muscle tissue burns more calories at rest than fat tissue. This is why resistance training is often recommended for increasing metabolism.
- Age: Metabolism naturally slows down as we age, largely due to hormonal changes and muscle loss.
- Genetics: Some individuals naturally have a faster or slower metabolic rate.
- Hormones: Thyroid issues (hypothyroidism or hyperthyroidism) can significantly alter RMR.
- Climate: Living in extreme cold or heat can force the body to work harder to maintain internal temperature, slightly increasing RMR.
How to Use This Number
Your RMR is not your calorie limit for the day; it is the minimum. To find out how many calories you burn in a typical day (your Maintenance Calories), you must multiply your RMR by an activity factor:
- Sedentary (desk job): RMR × 1.2
- Light Exercise (1-3 days/week): RMR × 1.375
- Moderate Exercise (3-5 days/week): RMR × 1.55
- Heavy Exercise (6-7 days/week): RMR × 1.725
- Athlete (2x per day): RMR × 1.9
Use the calculator above to establish your baseline, then adjust your intake based on your activity level and health goals.