function toggleUnits() {
var metricInputs = document.getElementById('metricInputs');
var imperialInputs = document.getElementById('imperialInputs');
var unitMetric = document.getElementById('unitMetric');
if (unitMetric.checked) {
metricInputs.style.display = 'block';
imperialInputs.style.display = 'none';
} else {
metricInputs.style.display = 'none';
imperialInputs.style.display = 'block';
}
// Clear results when units are toggled
document.getElementById('bmiValue').innerHTML = ";
document.getElementById('bmiCategory').innerHTML = ";
document.getElementById('healthyWeightRange').innerHTML = ";
}
function calculateBMI() {
var weight, heightCm, heightFt, heightIn, totalInches;
var bmi;
var unitSystem = document.querySelector('input[name="unitSystem"]:checked').value;
var resultDiv = document.getElementById('bmiResult');
var bmiValueElement = document.getElementById('bmiValue');
var bmiCategoryElement = document.getElementById('bmiCategory');
var healthyWeightRangeElement = document.getElementById('healthyWeightRange');
bmiValueElement.innerHTML = ";
bmiCategoryElement.innerHTML = ";
healthyWeightRangeElement.innerHTML = ";
if (unitSystem === 'metric') {
weight = parseFloat(document.getElementById('weightKg').value);
heightCm = parseFloat(document.getElementById('heightCm').value);
if (isNaN(weight) || isNaN(heightCm) || weight <= 0 || heightCm <= 0) {
bmiValueElement.innerHTML = 'Please enter valid positive numbers for weight and height.';
return;
}
var heightM = heightCm / 100;
bmi = weight / (heightM * heightM);
var minHealthyWeightKg = 18.5 * (heightM * heightM);
var maxHealthyWeightKg = 24.9 * (heightM * heightM);
healthyWeightRangeElement.innerHTML = 'A healthy weight for your height is typically between ' + minHealthyWeightKg.toFixed(1) + ' kg and ' + maxHealthyWeightKg.toFixed(1) + ' kg.';
} else { // imperial
weight = parseFloat(document.getElementById('weightLbs').value);
heightFt = parseFloat(document.getElementById('heightFt').value);
heightIn = parseFloat(document.getElementById('heightIn').value);
if (isNaN(weight) || isNaN(heightFt) || isNaN(heightIn) || weight <= 0 || (heightFt <= 0 && heightIn <= 0)) {
bmiValueElement.innerHTML = 'Please enter valid positive numbers for weight and height.';
return;
}
totalInches = (heightFt * 12) + heightIn;
if (totalInches <= 0) {
bmiValueElement.innerHTML = 'Please enter a valid positive height.';
return;
}
bmi = (weight / (totalInches * totalInches)) * 703;
var heightM_from_inches = totalInches * 0.0254; // Convert total inches to meters
var minHealthyWeightKg_from_m = 18.5 * (heightM_from_inches * heightM_from_inches);
var maxHealthyWeightKg_from_m = 24.9 * (heightM_from_inches * heightM_from_inches);
var minHealthyWeightLbs = minHealthyWeightKg_from_m * 2.20462;
var maxHealthyWeightLbs = maxHealthyWeightKg_from_m * 2.20462;
healthyWeightRangeElement.innerHTML = 'A healthy weight for your height is typically between ' + minHealthyWeightLbs.toFixed(1) + ' lbs and ' + maxHealthyWeightLbs.toFixed(1) + ' lbs.';
}
var category = ";
var categoryColor = ";
if (bmi = 18.5 && bmi = 25 && bmi <= 29.9) {
category = 'Overweight';
categoryColor = '#fd7e14'; // Orange
} else {
category = 'Obese';
categoryColor = '#dc3545'; // Red
}
bmiValueElement.innerHTML = 'Your BMI: ' + bmi.toFixed(2) + '';
bmiCategoryElement.innerHTML = 'Category: ' + category + '';
}
// Initialize unit display on load
document.addEventListener('DOMContentLoaded', function() {
toggleUnits();
});
Understanding Your Appropriate Weight
The concept of "appropriate weight" is often assessed using the Body Mass Index (BMI). BMI is a simple calculation that uses your height and weight to estimate if you are underweight, normal weight, overweight, or obese.
What is BMI?
Body Mass Index (BMI) is a measure that screens for weight categories that may lead to health problems. It's calculated by dividing a person's weight by the square of their height. While it's a widely used screening tool, it doesn't directly measure body fat or overall health.
Our calculator allows you to input your measurements in either metric or imperial units and performs the conversion and calculation for you.
BMI Categories:
Underweight: BMI less than 18.5
Normal weight: BMI between 18.5 and 24.9
Overweight: BMI between 25 and 29.9
Obese: BMI of 30 or greater
Limitations of BMI:
While BMI is a useful screening tool, it has limitations:
Muscle Mass: Athletes or individuals with high muscle mass may have a high BMI without being overweight, as muscle weighs more than fat.
Body Composition: BMI doesn't distinguish between fat and muscle. Two people with the same BMI might have very different body compositions.
Age and Gender: BMI ranges are generally the same for men and women, but body fat distribution can vary. Older adults may have more body fat than younger adults with the same BMI.
Ethnicity: Different ethnic groups may have different health risks at the same BMI.
What to do with your BMI result:
Your BMI result provides a general indication of your weight status. If your BMI falls outside the "Normal weight" range, it's a good idea to discuss it with a healthcare professional. They can provide a more comprehensive assessment of your health, considering factors like body composition, waist circumference, diet, physical activity, and family history, to determine the most appropriate weight and health goals for you.
Example Calculation:
Let's say a person weighs 70 kg and is 1.75 meters (175 cm) tall.
BMI = 70 kg / (1.75 m * 1.75 m)
BMI = 70 / 3.0625
BMI ≈ 22.86
This BMI of 22.86 falls within the "Normal weight" category (18.5 – 24.9).
For the same person, a healthy weight range would be: