Calculate Bmi with Height and Weight

Body Mass Index (BMI) Calculator

Metric (kg, cm) Imperial (lbs, ft, in)

function toggleUnits() { var unitSystem = document.getElementById("unitSystem").value; if (unitSystem === "metric") { document.getElementById("metricInputs").style.display = "block"; document.getElementById("imperialInputs").style.display = "none"; } else { document.getElementById("metricInputs").style.display = "none"; document.getElementById("imperialInputs").style.display = "block"; } } function calculateBMI() { var unitSystem = document.getElementById("unitSystem").value; var bmi; var resultDiv = document.getElementById("bmiResult"); resultDiv.innerHTML = ""; // Clear previous result resultDiv.style.backgroundColor = "#e9f7ef"; // Reset background color resultDiv.style.color = "#155724"; // Reset text color if (unitSystem === "metric") { var weight = parseFloat(document.getElementById("weightKg").value); var height = parseFloat(document.getElementById("heightCm").value); if (isNaN(weight) || isNaN(height) || weight <= 0 || height <= 0) { resultDiv.innerHTML = "Please enter valid positive numbers for weight (kg) and height (cm)."; resultDiv.style.backgroundColor = "#f8d7da"; resultDiv.style.color = "#721c24"; return; } var heightM = height / 100; // Convert cm to meters bmi = weight / (heightM * heightM); } else { // Imperial var weightLbs = parseFloat(document.getElementById("weightLbs").value); var heightFeet = parseFloat(document.getElementById("heightFeet").value); var heightInches = parseFloat(document.getElementById("heightInches").value); if (isNaN(weightLbs) || isNaN(heightFeet) || isNaN(heightInches) || weightLbs <= 0 || (heightFeet <= 0 && heightInches <= 0)) { resultDiv.innerHTML = "Please enter valid positive numbers for weight (lbs) and height (feet/inches)."; resultDiv.style.backgroundColor = "#f8d7da"; resultDiv.style.color = "#721c24"; return; } var totalInches = (heightFeet * 12) + heightInches; bmi = (weightLbs / (totalInches * totalInches)) * 703; } if (isNaN(bmi)) { resultDiv.innerHTML = "An error occurred during calculation. Please check your inputs."; resultDiv.style.backgroundColor = "#f8d7da"; resultDiv.style.color = "#721c24"; return; } var bmiCategory; if (bmi = 18.5 && bmi = 25 && bmi < 29.9) { bmiCategory = "Overweight"; } else { bmiCategory = "Obese"; } resultDiv.innerHTML = "Your BMI is: " + bmi.toFixed(2) + ""; resultDiv.innerHTML += "Category: " + bmiCategory + ""; } // Initialize unit display on page load window.onload = function() { toggleUnits(); };

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 relation 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 BMI is Calculated

The BMI calculation uses a straightforward formula that takes into account your weight and height. The formula varies slightly depending on whether you use metric or imperial units.

Metric Formula:

BMI = weight (kg) / (height (m) * height (m))

To use this formula, your height must be in meters. If you measure your height in centimeters, you'll need to divide it by 100 to convert it to meters.

Example (Metric):

• Weight: 70 kg
• Height: 175 cm (1.75 m)
• BMI = 70 / (1.75 * 1.75) = 70 / 3.0625 = 22.86

Imperial Formula:

BMI = (weight (lbs) / (height (inches) * height (inches))) * 703

For this formula, your weight should be in pounds and your height in inches. The factor of 703 is used to convert the units appropriately.

Example (Imperial):

• Weight: 150 lbs
• Height: 5 feet 9 inches (which is 69 inches)
• BMI = (150 / (69 * 69)) * 703 = (150 / 4761) * 703 = 0.0315 * 703 = 22.15

BMI Categories for Adults

Once your BMI is calculated, it falls into one of the following categories established by the World Health Organization (WHO) for adults aged 20 and older:

• 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 guide to help assess health risks associated with weight.

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 or individuals with high muscle mass may have a high BMI, classifying them as "overweight" or "obese" even if their body fat percentage is low and they are very healthy.
• Age and Sex: BMI ranges are generally the same for adult men and women, but body composition changes with age. Older adults may have less muscle mass and more fat than younger adults, even with the same BMI.
• Ethnicity: Different ethnic groups may have different associations between BMI, body fat percentage, and health risks. For example, some Asian populations may have higher health risks at lower BMIs compared to Caucasians.
• Body Composition: BMI doesn't account for fat distribution. Abdominal fat (around the waist) is associated with higher health risks than fat stored in other areas. Waist circumference can be a better indicator of abdominal fat.
• Children and Adolescents: BMI is interpreted differently for children and adolescents, using age- and sex-specific percentile charts rather than fixed categories.

Conclusion

The BMI calculator is a convenient tool for a quick assessment of your weight status. However, it should always be used as a starting point for discussion with a healthcare professional. For a comprehensive understanding of your health and ideal weight, factors like body fat percentage, waist circumference, diet, physical activity levels, and family history should also be considered.