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Body Mass Index (BMI) Calculator

Your BMI:

Category:

function updateUnitLabels() { var weightLabel = document.getElementById('weightLabel'); var heightLabel = document.getElementById('heightLabel'); var weightInput = document.getElementById('weightInput'); var heightInput = document.getElementById('heightInput'); if (document.getElementById('unitMetric').checked) { weightLabel.textContent = 'Weight (kg):'; heightLabel.textContent = 'Height (cm):'; weightInput.placeholder = 'e.g., 70'; heightInput.placeholder = 'e.g., 175'; } else { weightLabel.textContent = 'Weight (lbs):'; heightLabel.textContent = 'Height (inches):'; weightInput.placeholder = 'e.g., 150'; heightInput.placeholder = 'e.g., 68'; } } function calculateBMI() { var weight = parseFloat(document.getElementById('weightInput').value); var height = parseFloat(document.getElementById('heightInput').value); var bmi; var category = "; document.getElementById('bmiResultContainer').style.display = 'none'; // Hide previous results if (isNaN(weight) || isNaN(height) || weight <= 0 || height <= 0) { document.getElementById('bmiResult').textContent = 'Invalid Input'; document.getElementById('bmiCategory').textContent = 'Please enter valid positive numbers for weight and height.'; document.getElementById('bmiResultContainer').style.backgroundColor = '#f8d7da'; // Error color document.getElementById('bmiResultContainer').style.display = 'block'; return; } if (document.getElementById('unitMetric').checked) { // Metric: BMI = weight (kg) / (height (m) * height (m)) var heightMeters = height / 100; bmi = weight / (heightMeters * heightMeters); } else { // Imperial: BMI = (weight (lbs) / (height (in) * height (in))) * 703 bmi = (weight / (height * height)) * 703; } bmi = bmi.toFixed(2); // Round to 2 decimal places if (bmi = 18.5 && bmi = 25.0 && bmi <= 29.9) { category = 'Overweight'; document.getElementById('bmiCategory').style.color = '#fd7e14'; // Orange } else { category = 'Obese'; document.getElementById('bmiCategory').style.color = '#dc3545'; // Red } document.getElementById('bmiResult').textContent = bmi; document.getElementById('bmiCategory').textContent = category; document.getElementById('bmiResultContainer').style.backgroundColor = '#e9f7ef'; // Reset to success color document.getElementById('bmiResultContainer').style.display = 'block'; } // Initialize labels on page load window.onload = updateUnitLabels;

Understanding Your Body Mass Index (BMI)

The Body Mass Index (BMI) is a simple numerical measure that is widely used to classify whether an individual's weight is healthy in proportion to their height. Developed by Adolphe Quetelet in the 19th century, it serves as a screening tool to identify potential weight problems for adults.

How is BMI Calculated?

The calculation for BMI is straightforward, though it varies slightly depending on whether you use the metric or imperial system:

• Metric System: BMI = weight (kg) / (height (m)²)
• Imperial System: BMI = (weight (lbs) / (height (inches)²)) × 703

Our calculator above allows you to easily switch between these two systems to find your BMI.

What Do Your BMI Results Mean?

Once your BMI is calculated, it falls into one of several categories:

• Underweight: BMI less than 18.5
• Normal weight: BMI between 18.5 and 24.9
• Overweight: BMI between 25.0 and 29.9
• Obese: BMI of 30.0 or greater

Examples:

• Metric Example: If you weigh 70 kg and are 175 cm (1.75 m) tall, your BMI would be 70 / (1.75 * 1.75) = 22.86. This falls into the Normal weight category.
• Imperial Example: If you weigh 150 lbs and are 68 inches tall, your BMI would be (150 / (68 * 68)) * 703 = 22.8. This also falls into the Normal weight category.

Limitations of BMI

While BMI is a useful screening tool, it's important to understand its limitations:

• Muscle Mass: BMI does not distinguish between muscle and fat. Athletes with high muscle mass may have a high BMI, classifying them as "overweight" or "obese" even if their body fat percentage is low.
• Age and Sex: BMI ranges are generally the same for men and women, but body composition changes with age. Older adults may have less muscle mass and more fat than younger adults with the same BMI.
• Body Fat Distribution: BMI doesn't account for where body fat is stored. Abdominal fat (around the waist) is considered more dangerous than fat stored in the hips and thighs.
• Ethnicity: Different ethnic groups may have different healthy BMI ranges.

When to Consult a Professional

BMI is a good starting point for assessing your weight status, but it should not be the only measure. For a comprehensive understanding of your health and ideal weight, it's always best to consult with a healthcare professional. They can consider other factors like body composition, waist circumference, diet, physical activity levels, and family history to provide personalized advice.