Calculate your Basal Metabolic Rate (BMR) and Body Mass Index (BMI) based on your personal metrics.
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Enter your details to see your results.
Understanding Your Health Metrics: BMR and BMI
Maintaining an optimal weight and understanding your body's basic energy needs are fundamental aspects of personal health. This calculator provides two key metrics: Basal Metabolic Rate (BMR) and Body Mass Index (BMI). These figures can serve as starting points for assessing your current health status and planning for fitness or weight management goals.
Basal Metabolic Rate (BMR)
Your BMR is the minimum number of calories your body needs to perform essential functions like breathing, circulating blood, and maintaining body temperature while at rest. It's essentially the energy your body burns to stay alive. Factors such as age, sex, weight, and height significantly influence BMR. A higher muscle mass generally leads to a higher BMR.
We use the Mifflin-St Jeor equation, which is widely considered one of the most accurate formulas for estimating BMR:
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
It's important to note that BMR accounts for only the calories burned at rest. Your total daily energy expenditure (TDEE) will be higher, as it also includes calories burned through physical activity.
Body Mass Index (BMI)
BMI is a screening tool used to estimate whether an individual has a healthy weight for their height. It is calculated using a simple formula that relates weight to height. While it doesn't measure body fat directly or account for muscle mass, it is a useful indicator for categorizing weight status.
The formula for BMI is:
BMI = (weight in kg) / (height in meters)²
To use this formula with height in centimeters, you must first convert height to meters by dividing by 100 (e.g., 175 cm = 1.75 meters).
BMI Categories (WHO Standards):
Below 18.5: Underweight
18.5 – 24.9: Normal weight
25.0 – 29.9: Overweight
30.0 and above: Obesity
Disclaimer: This calculator is for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
function calculateHealthMetrics() {
var age = parseFloat(document.getElementById("age").value);
var weight = parseFloat(document.getElementById("weight").value);
var height = parseFloat(document.getElementById("height").value);
var gender = document.getElementById("gender").value;
var resultTextElement = document.getElementById("result-text");
var resultDiv = document.getElementById("result");
// Clear previous results and styling
resultTextElement.innerHTML = "";
resultDiv.style.backgroundColor = '#d4edda'; // Reset to default success green background
resultDiv.style.color = '#155724';
resultDiv.style.borderColor = '#c3e6cb';
// Input validation
if (isNaN(age) || age 120) {
resultTextElement.innerHTML = "Please enter a valid age.";
resultDiv.style.backgroundColor = '#f8d7da';
resultDiv.style.color = '#721c24';
resultDiv.style.borderColor = '#f5c6cb';
return;
}
if (isNaN(weight) || weight 1000) {
resultTextElement.innerHTML = "Please enter a valid weight (kg).";
resultDiv.style.backgroundColor = '#f8d7da';
resultDiv.style.color = '#721c24';
resultDiv.style.borderColor = '#f5c6cb';
return;
}
if (isNaN(height) || height 300) {
resultTextElement.innerHTML = "Please enter a valid height (cm).";
resultDiv.style.backgroundColor = '#f8d7da';
resultDiv.style.color = '#721c24';
resultDiv.style.borderColor = '#f5c6cb';
return;
}
// Calculate BMR (Mifflin-St Jeor Equation)
var bmr = 0;
if (gender === "male") {
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else { // female
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
// Calculate BMI
var heightInMeters = height / 100;
var bmi = weight / (heightInMeters * heightInMeters);
// Format BMI to one decimal place
bmi = bmi.toFixed(1);
// Determine BMI category
var bmiCategory = "";
if (bmi = 18.5 && bmi = 25 && bmi <= 29.9) {
bmiCategory = "Overweight";
} else {
bmiCategory = "Obesity";
}
// Display results
resultTextElement.innerHTML =
"Your BMR is approximately " + Math.round(bmr) + " calories/day. " +
"Your BMI is " + bmi + " (" + bmiCategory + ").";
// Optional: Add visual feedback for BMI category if desired, but keeping it clean for now.
}