Calculate Adult Body Mass Index based on CDC Standards
Standard (lb/in)
Metric (kg/cm)
Your BMI is:
—
—
Understanding Your BMI Result
The Body Mass Index (BMI) is a screening tool used by the Center for Disease Control (CDC) to identify possible weight problems for adults. While BMI does not measure body fat directly, it is moderately correlated with more direct measures of body fat. Furthermore, BMI is strongly correlated with various metabolic and disease outcomes.
CDC BMI Categories for Adults
BMI Range
Weight Status
Below 18.5
Underweight
18.5 – 24.9
Healthy Weight
25.0 – 29.9
Overweight
30.0 or Higher
Obese
How BMI is Calculated
The CDC uses two primary formulas depending on the measurement system used:
Standard (Imperial): [Weight (lbs) / Height (inches)²] x 703
Metric: Weight (kg) / Height (meters)²
Examples of BMI Calculations
Example 1 (Imperial): An individual who weighs 150 lbs and is 5'5″ (65 inches) tall.
Calculation: (150 / (65 x 65)) x 703 = 24.96 (Healthy Weight)
Example 2 (Metric): An individual who weighs 90 kg and is 180 cm tall.
Calculation: 90 / (1.8 x 1.8) = 27.78 (Overweight)
Important Note: BMI is a screening tool, not a diagnostic one. A high BMI may be a sign of high body fat, but it can also be influenced by muscle mass, bone density, and overall body composition. Always consult with a healthcare professional for a complete health assessment.
function updateUnits() {
var system = document.getElementById('unitSystem').value;
var wLabel = document.getElementById('weightLabel');
var hLabel = document.getElementById('heightLabel');
var wInput = document.getElementById('bmiWeight');
var hInput = document.getElementById('bmiHeight');
if (system === 'metric') {
wLabel.innerText = 'Weight (kg)';
hLabel.innerText = 'Height (cm)';
wInput.placeholder = 'e.g., 70';
hInput.placeholder = 'e.g., 175';
} else {
wLabel.innerText = 'Weight (lbs)';
hLabel.innerText = 'Height (inches)';
wInput.placeholder = 'e.g., 160';
hInput.placeholder = 'e.g., 68';
}
document.getElementById('bmiResultWrapper').style.display = 'none';
}
function calculateBMI() {
var system = document.getElementById('unitSystem').value;
var weight = parseFloat(document.getElementById('bmiWeight').value);
var height = parseFloat(document.getElementById('bmiHeight').value);
var resultValue = document.getElementById('bmiValue');
var resultCategory = document.getElementById('bmiCategory');
var resultDesc = document.getElementById('bmiDescription');
var wrapper = document.getElementById('bmiResultWrapper');
if (isNaN(weight) || isNaN(height) || weight <= 0 || height <= 0) {
alert("Please enter valid positive numbers for height and weight.");
return;
}
var bmi = 0;
if (system === 'metric') {
// Formula: kg / (m^2)
var heightInMeters = height / 100;
bmi = weight / (heightInMeters * heightInMeters);
} else {
// Formula: (lbs / in^2) * 703
bmi = (weight / (height * height)) * 703;
}
var roundedBMI = bmi.toFixed(1);
resultValue.innerText = roundedBMI;
var category = "";
var color = "";
var textColor = "#fff";
var desc = "";
if (bmi = 18.5 && bmi = 25 && bmi < 30) {
category = "Overweight";
color = "#ff9800";
desc = "Your BMI falls within the overweight range. This can increase the risk for certain health issues.";
} else {
category = "Obese";
color = "#f44336";
desc = "Your BMI falls within the obese range. People in this category may be at higher risk for heart disease, type 2 diabetes, and certain cancers.";
}
resultCategory.innerText = category;
resultCategory.style.backgroundColor = color;
resultCategory.style.color = textColor;
resultDesc.innerText = desc;
wrapper.style.display = 'block';
wrapper.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}