Calculate your Body Mass Index (BMI) and get insight into how muscle mass might influence your health assessment.
Metric (kg, cm)
Imperial (lbs, inches)
Understanding BMI and Muscle Mass
Body Mass Index (BMI) is a widely used tool to broadly categorize a person's weight in relation to their height. It's calculated by dividing a person's weight by the square of their height. While simple and convenient, BMI has limitations, especially for individuals with significant muscle mass.
For example, if you weigh 70 kg and are 1.75 meters tall, your BMI is 70 / (1.75 * 1.75) = 22.86.
Why Muscle Mass Matters
Muscle is denser than fat. This means a very muscular individual might have a higher weight and thus a higher BMI, even if they have a very low body fat percentage and are considered healthy. In such cases, a high BMI might incorrectly suggest overweight or obesity, when in reality, the individual is lean and athletic.
BMI Categories (WHO):
Underweight: BMI < 18.5
Normal weight: BMI 18.5 – 24.9
Overweight: BMI 25 – 29.9
Obesity: BMI ≥ 30
For athletes or individuals with high muscle mass, it's advisable to consider BMI alongside other health indicators such as body fat percentage, waist circumference, and overall fitness levels. This calculator provides the standard BMI, but remember to interpret the results in the context of your own physique and lifestyle.
function calculateBMI() {
var weightInput = document.getElementById("weight");
var heightInput = document.getElementById("height");
var unitSystemSelect = document.getElementById("unitSystem");
var resultDiv = document.getElementById("result");
var weight = parseFloat(weightInput.value);
var height = parseFloat(heightInput.value);
var unitSystem = unitSystemSelect.value;
// Input validation
if (isNaN(weight) || weight <= 0) {
resultDiv.innerHTML = "Please enter a valid weight.";
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#dc3545"; // Red for error
return;
}
if (isNaN(height) || height 300) { // Assuming height in cm is not more than 300
resultDiv.innerHTML = "Please check your height in cm. It seems unusually high.";
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#dc3545";
return;
}
var heightInMeters = height / 100;
bmi = weight / (heightInMeters * heightInMeters);
} else {
// Imperial: weight in lbs, height in inches
if (height > 120) { // Assuming height in inches is not more than 120
resultDiv.innerHTML = "Please check your height in inches. It seems unusually high.";
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#dc3545";
return;
}
bmi = (weight / (height * height)) * 703;
}
// Round BMI to two decimal places
bmi = Math.round(bmi * 100) / 100;
// Determine BMI category
if (bmi = 18.5 && bmi = 25 && bmi <= 29.9) {
bmiCategory = "Overweight";
} else {
bmiCategory = "Obese";
}
resultDiv.innerHTML = bmi + "" + bmiCategory + "";
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#28a745"; // Green for success
}