Estimate how many calories your body burns at rest.
Male
Female
Sedentary (little or no exercise)
Lightly Active (exercise 1-3 days/week)
Moderately Active (exercise 3-5 days/week)
Very Active (exercise 6-7 days/week)
Extra Active (very hard exercise/physical job)
Resting Metabolic Rate (RMR):–
Daily Calories to Maintain Weight (TDEE):–
Understanding Your Resting Metabolic Rate
Calculating "my resting metabolic rate" (RMR) is the first fundamental step in designing a nutrition plan tailored to your specific physiological needs. RMR represents the total number of calories your body burns while at complete rest to maintain basic vital functions such as breathing, circulating blood, and organ function. Even if you laid in bed all day without moving, your body would still require this specific amount of energy to survive.
How the RMR Calculator Works
This calculator utilizes the Mifflin-St Jeor equation, widely considered by dietitians and health professionals to be the most reliable formula for estimating calorie needs in healthy adults. The formula accounts for:
Weight: Heavier bodies generally require more energy to maintain.
Height: Taller individuals typically have a larger body surface area, increasing metabolic burn.
Age: As we age, metabolic rate tends to naturally decrease, primarily due to a gradual loss of muscle mass.
Gender: Men typically have a higher muscle-to-fat ratio than women, resulting in a slightly higher baseline metabolic rate.
RMR vs. BMR: What is the Difference?
You may often see the terms RMR (Resting Metabolic Rate) and BMR (Basal Metabolic Rate) used interchangeably, but there is a slight technical difference. BMR is measured under very strict laboratory conditions (immediately upon waking, in a darkened room, after 12 hours of fasting). RMR is measured under less restrictive conditions and is essentially the practical application of BMR. For most people using online calculators, the difference in the resulting number is negligible.
From RMR to TDEE
While your RMR tells you what you burn at rest, your Total Daily Energy Expenditure (TDEE) tells you how many calories you burn in a real day, including movement and exercise. This calculator multiplies your RMR by an "Activity Factor" to estimate your TDEE:
Sedentary (1.2): Desk job, little to no intentional exercise.
Lightly Active (1.375): Light exercise or sports 1-3 days a week.
Moderately Active (1.55): Moderate exercise or sports 3-5 days a week.
Very Active (1.725): Hard exercise or sports 6-7 days a week.
Extra Active (1.9): Very hard exercise, physical job, or training twice a day.
Using Your Results
Once you have your TDEE from the calculator above, you can plan your caloric intake based on your goals:
Weight Loss: Aim to eat 300-500 calories below your TDEE.
Maintenance: Eat an amount equal to your TDEE.
Muscle Gain: Aim to eat 250-500 calories above your TDEE.
// Global variable to track current unit system
var currentUnit = 'metric';
function toggleUnits() {
var radios = document.getElementsByName('unitSystem');
for (var i = 0; i < radios.length; i++) {
if (radios[i].checked) {
currentUnit = radios[i].value;
break;
}
}
var metricWeight = document.getElementById('metricWeightBox');
var imperialWeight = document.getElementById('imperialWeightBox');
var metricHeight = document.getElementById('metricHeightBox');
var imperialHeight = document.getElementById('imperialHeightBox');
if (currentUnit === 'imperial') {
metricWeight.style.display = 'none';
imperialWeight.style.display = 'block';
metricHeight.style.display = 'none';
imperialHeight.style.display = 'block';
} else {
metricWeight.style.display = 'block';
imperialWeight.style.display = 'none';
metricHeight.style.display = 'block';
imperialHeight.style.display = 'none';
}
}
function calculateRMR() {
// 1. Gather Inputs
var gender = document.getElementById('gender').value;
var age = parseFloat(document.getElementById('age').value);
var activityMultiplier = parseFloat(document.getElementById('activityLevel').value);
var weightInKg = 0;
var heightInCm = 0;
// 2. Normalize inputs to Metric for Calculation
if (currentUnit === 'metric') {
weightInKg = parseFloat(document.getElementById('weightKg').value);
heightInCm = parseFloat(document.getElementById('heightCm').value);
} else {
var weightLbs = parseFloat(document.getElementById('weightLbs').value);
var heightFt = parseFloat(document.getElementById('heightFt').value);
var heightIn = parseFloat(document.getElementById('heightIn').value);
// Validation for imperial inputs
if (isNaN(weightLbs) || isNaN(heightFt)) {
alert("Please enter valid numbers for weight and height.");
return;
}
if (isNaN(heightIn)) heightIn = 0; // handle empty inches
// Conversion
weightInKg = weightLbs * 0.453592;
heightInCm = (heightFt * 30.48) + (heightIn * 2.54);
}
// 3. Validation
if (isNaN(age) || isNaN(weightInKg) || isNaN(heightInCm) || age <= 0 || weightInKg <= 0 || heightInCm <= 0) {
alert("Please fill in all fields with valid positive numbers.");
return;
}
// 4. Calculate RMR (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 = (10 * weightInKg) + (6.25 * heightInCm) – (5 * age);
if (gender === 'male') {
rmr += 5;
} else {
rmr -= 161;
}
// 5. Calculate TDEE
var tdee = rmr * activityMultiplier;
// 6. Display Results
var resultDiv = document.getElementById('results');
var rmrDisplay = document.getElementById('rmrResult');
var tdeeDisplay = document.getElementById('tdeeResult');
rmrDisplay.innerHTML = Math.round(rmr) + " Calories/day";
tdeeDisplay.innerHTML = Math.round(tdee) + " Calories/day";
resultDiv.style.display = 'block';
// Scroll to results
resultDiv.scrollIntoView({behavior: "smooth"});
}