function toggleUnits() {
var radios = document.getElementsByName('units');
var metricDiv = document.getElementById('metric-inputs');
var imperialDiv = document.getElementById('imperial-inputs');
var selectedValue;
for (var i = 0; i < radios.length; i++) {
if (radios[i].checked) {
selectedValue = radios[i].value;
break;
}
}
if (selectedValue === 'imperial') {
metricDiv.style.display = 'none';
imperialDiv.style.display = 'block';
} else {
metricDiv.style.display = 'block';
imperialDiv.style.display = 'none';
}
}
function calculateBMR() {
// Get common values
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;
break;
}
}
// Get Unit system
var unitRadios = document.getElementsByName('units');
var unit = 'metric';
for (var j = 0; j < unitRadios.length; j++) {
if (unitRadios[j].checked) {
unit = unitRadios[j].value;
break;
}
}
var weight = 0; // in kg
var height = 0; // in cm
var isValid = true;
if (isNaN(age) || age < 1) {
alert("Please enter a valid age.");
isValid = false;
}
if (unit === 'metric') {
var wKg = parseFloat(document.getElementById('weightKg').value);
var hCm = parseFloat(document.getElementById('heightCm').value);
if (isNaN(wKg) || isNaN(hCm)) {
alert("Please enter valid weight and height values.");
isValid = false;
} else {
weight = wKg;
height = hCm;
}
} else {
var wLbs = parseFloat(document.getElementById('weightLbs').value);
var hFt = parseFloat(document.getElementById('heightFt').value);
var hIn = parseFloat(document.getElementById('heightIn').value);
// Handle missing inches as 0 if feet is provided
if (isNaN(hIn)) hIn = 0;
if (isNaN(wLbs) || isNaN(hFt)) {
alert("Please enter valid weight and height values.");
isValid = false;
} else {
// Convert Imperial to Metric
weight = wLbs * 0.453592;
height = (hFt * 30.48) + (hIn * 2.54);
}
}
if (isValid) {
// Mifflin-St Jeor Equation
var bmr = 0;
// Formula: (10 * weight) + (6.25 * height) – (5 * age) + s
// s is +5 for males and -161 for females
var baseCalc = (10 * weight) + (6.25 * height) – (5 * age);
if (gender === 'male') {
bmr = baseCalc + 5;
} else {
bmr = baseCalc – 161;
}
// Display Result
var resultDiv = document.getElementById('result');
var bmrValueSpan = document.getElementById('bmrValue');
bmrValueSpan.innerHTML = Math.round(bmr).toLocaleString();
resultDiv.style.display = 'block';
}
}
What Is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate (BMR) represents the number of calories your body needs to accomplish its most basic (basal) life-sustaining functions. These functions include breathing, circulation, nutrient processing, and cell production. Essentially, your BMR is the amount of energy (calories) you would burn if you stayed in bed all day without moving.
Understanding "what is basal metabolic rate calculator" functionality helps in establishing a baseline for weight management. Your BMR accounts for approximately 60% to 75% of your total daily calorie expenditure (TDEE). The remaining calories are burned through physical activity and the digestion of food.
How the Calculation Works
This calculator utilizes the Mifflin-St Jeor Equation, which is currently considered the most accurate formula for estimating BMR in clinical settings. The calculation relies on four specific variables:
Weight: Heavier individuals require more energy to maintain their body mass.
Height: Taller individuals generally have a larger skin surface area and lean body mass, increasing metabolic rate.
Age: Metabolic rate typically decreases as you age, primarily due to a loss of muscle mass.
Gender: Men generally have a higher BMR than women because they tend to have more lean muscle mass and less body fat.
Using Your BMR for Weight Goals
Once you know your BMR, you can calculate your Total Daily Energy Expenditure (TDEE) by multiplying your BMR by an activity factor ranging from 1.2 (sedentary) to 1.9 (extremely active). To lose weight, you generally aim to consume fewer calories than your TDEE; to gain weight, you consume more.
Note: While this calculator provides a reliable estimate, individual metabolic rates can vary based on genetics, hormonal health, and body composition (muscle-to-fat ratio).