Body Weight Calculator

Body Mass Index (BMI) Calculator

Use this calculator to determine your Body Mass Index (BMI) and find out if you are in a healthy weight range for your height.

function updateUnitLabels() { var unitSystem = document.querySelector('input[name="unitSystem"]:checked').value; if (unitSystem === 'metric') { document.getElementById('weightLabel').innerText = 'Weight (kg):'; document.getElementById('heightLabel').innerText = 'Height (cm):'; document.getElementById('weightInput').placeholder = 'e.g., 70'; document.getElementById('heightInput').placeholder = 'e.g., 175'; } else { document.getElementById('weightLabel').innerText = 'Weight (lbs):'; document.getElementById('heightLabel').innerText = 'Height (inches):'; document.getElementById('weightInput').placeholder = 'e.g., 150'; document.getElementById('heightInput').placeholder = 'e.g., 68'; } // Clear previous results when units change document.getElementById('bmiResult').innerHTML = "; } function calculateBMI() { var weight = parseFloat(document.getElementById('weightInput').value); var height = parseFloat(document.getElementById('heightInput').value); var unitSystem = document.querySelector('input[name="unitSystem"]:checked').value; var resultDiv = document.getElementById('bmiResult'); resultDiv.innerHTML = "; // Clear previous results if (isNaN(weight) || isNaN(height) || weight <= 0 || height <= 0) { resultDiv.innerHTML = 'Please enter valid positive numbers for weight and height.'; return; } var bmi; var heightInMeters; if (unitSystem === 'metric') { heightInMeters = height / 100; // Convert cm to meters bmi = weight / (heightInMeters * heightInMeters); } else { // Imperial // BMI = (weight (lbs) / (height (inches))^2) * 703 bmi = (weight / (height * height)) * 703; } var bmiCategory; if (bmi = 18.5 && bmi = 25 && bmi < 29.9) { bmiCategory = 'Overweight'; } else { bmiCategory = 'Obese'; } resultDiv.innerHTML = 'Your BMI is: ' + bmi.toFixed(2) + '' + 'Category: ' + bmiCategory + ''; } // Initialize labels on page load window.onload = updateUnitLabels; .calculator-container { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: #f9f9f9; padding: 25px; border-radius: 10px; box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1); max-width: 500px; margin: 20px auto; border: 1px solid #e0e0e0; } .calculator-container h2 { color: #333; text-align: center; margin-bottom: 20px; font-size: 1.8em; } .calculator-container p { color: #555; line-height: 1.6; margin-bottom: 15px; } .form-group { margin-bottom: 18px; } .form-group label { display: block; margin-bottom: 8px; color: #444; font-weight: bold; font-size: 0.95em; } .form-group input[type="number"] { width: calc(100% – 22px); padding: 12px; border: 1px solid #ccc; border-radius: 6px; font-size: 1em; box-sizing: border-box; transition: border-color 0.3s ease; } .form-group input[type="number"]:focus { border-color: #007bff; outline: none; box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.25); } .form-group input[type="radio"] { margin-right: 8px; } .form-group label input[type="radio"] { margin-right: 5px; vertical-align: middle; } button { background-color: #007bff; color: white; padding: 12px 25px; border: none; border-radius: 6px; cursor: pointer; font-size: 1.1em; width: 100%; transition: background-color 0.3s ease, transform 0.2s ease; margin-top: 10px; } button:hover { background-color: #0056b3; transform: translateY(-1px); } button:active { transform: translateY(0); } .calculator-result { margin-top: 25px; padding: 15px; background-color: #e9f7ef; border: 1px solid #d4edda; border-radius: 8px; color: #155724; font-size: 1.1em; text-align: center; } .calculator-result p { margin: 5px 0; font-weight: normal; } .calculator-result strong { color: #007bff; font-weight: bold; }

Understanding Your Body Mass Index (BMI)

The Body Mass Index (BMI) is a simple numerical measure that is commonly used to classify whether an individual's weight is healthy in relation to their height. It's a widely accepted screening tool for potential weight problems for adults, but it does not diagnose body fatness or health directly.

How BMI is Calculated

The BMI is calculated using a straightforward formula:

• Metric Formula: BMI = weight (kg) / [height (m)]²
• Imperial Formula: BMI = [weight (lbs) / [height (inches)]²] x 703

Our calculator allows you to input your weight and height in either metric (kilograms and centimeters) or imperial (pounds and inches) units, and it will automatically perform the necessary conversions and calculations for you.

BMI Categories for Adults

For adults aged 20 and older, BMI is interpreted using standard weight status categories:

• Underweight: Less than 18.5
• Normal weight: 18.5 – 24.9
• Overweight: 25.0 – 29.9
• Obese: 30.0 or greater

These categories provide a general guideline. For example, if you weigh 70 kg and are 175 cm (1.75 m) tall, your BMI would be calculated as 70 / (1.75 * 1.75) = 22.86, placing you in the 'Normal weight' category.

Limitations of BMI

While BMI is a useful screening tool, it has limitations:

• Muscle Mass: It doesn't 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 Gender: BMI interpretations can vary for children and adolescents, and body composition naturally changes with age and gender.
• Body Fat Distribution: BMI doesn't account for where fat is stored. Abdominal fat, for instance, is associated with higher health risks than fat stored in the hips and thighs.
• Ethnicity: Different ethnic groups may have different health risks at the same BMI.

Therefore, BMI should be used as one of many tools to assess health. A healthcare provider can offer a more comprehensive assessment by considering other factors like waist circumference, body fat percentage, diet, physical activity levels, and family history.

Why Calculate Your BMI?

Knowing your BMI can be a good starting point for understanding your general health status. It can help you and your doctor identify potential risks associated with being underweight, overweight, or obese, which are linked to various health conditions such as heart disease, diabetes, and certain cancers. It's a simple, non-invasive way to monitor your weight over time and make informed decisions about your health and lifestyle.