Calculate your BMI using your weight in kilograms and height in centimeters.
Your BMI will appear here.
Understanding Your Body Mass Index (BMI)
Body Mass Index (BMI) is a simple, non-invasive method used to estimate a person's body fat percentage. It's calculated using a person's weight and height. While it doesn't directly measure body fat, it serves as a useful screening tool for categorizing weight into different health ranges: underweight, normal weight, overweight, and obese. This helps to identify potential weight-related health risks.
The BMI Formula
The standard formula for calculating BMI is:
BMI = weight (kg) / [height (m)]²
In this calculator, we ask for height in centimeters (cm) for convenience. To use the formula, height must be converted to meters (m) by dividing by 100. Therefore, if your height is 175 cm, it is 1.75 meters.
For example, if a person weighs 70 kg and is 175 cm (1.75 m) tall:
Convert height to meters: 175 cm / 100 = 1.75 m
Square the height in meters: 1.75 m * 1.75 m = 3.0625 m²
Calculate BMI: 70 kg / 3.0625 m² = 22.86
The resulting BMI is approximately 22.86.
BMI Categories (WHO Standards)
The World Health Organization (WHO) provides the following standard classifications for BMI ranges in adults:
Underweight: Below 18.5
Normal weight: 18.5 – 24.9
Overweight: 25 – 29.9
Obese: 30 or greater
Use Cases and Considerations
BMI is a widely used tool because it's inexpensive and easy to perform. It's a good starting point for assessing weight status and potential health risks associated with being underweight or overweight. However, it's important to remember that BMI is a screening tool, not a diagnostic tool.
Factors such as muscle mass, bone density, and body composition can affect the interpretation of BMI. For instance, individuals with high muscle mass (like athletes) might have a higher BMI that doesn't necessarily indicate excess body fat. Similarly, BMI doesn't distinguish between fat and muscle.
It's always recommended to consult with a healthcare professional for a comprehensive assessment of your health and weight status, especially if you have concerns. They can consider other factors beyond BMI to provide personalized advice.
function calculateBmi() {
var weightKgInput = document.getElementById("weightKg");
var heightCmInput = document.getElementById("heightCm");
var resultDiv = document.getElementById("result");
var weightKg = parseFloat(weightKgInput.value);
var heightCm = parseFloat(heightCmInput.value);
// Clear previous classes
resultDiv.className = "";
if (isNaN(weightKg) || isNaN(heightCm) || weightKg <= 0 || heightCm <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for weight and height.";
resultDiv.style.backgroundColor = "#ffc107"; /* Warning Yellow */
return;
}
var heightM = heightCm / 100; // Convert cm to meters
var bmi = weightKg / (heightM * heightM);
bmi = bmi.toFixed(2); // Round to two decimal places
var bmiCategory = "";
if (bmi = 18.5 && bmi = 25 && bmi <= 29.9) {
bmiCategory = "Overweight";
resultDiv.className = "overweight";
} else {
bmiCategory = "Obese";
resultDiv.className = "obese";
}
resultDiv.innerHTML = "Your BMI: " + bmi + " (" + bmiCategory + ")";
}