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Body Surface Area (BSA) Calculator

Mosteller (Recommended) DuBois and DuBois Haycock Gehan and George

function calculateBSA() { var weight = parseFloat(document.getElementById('bsaWeight').value); var height = parseFloat(document.getElementById('bsaHeight').value); var formula = document.getElementById('bsaFormula').value; var resultDiv = document.getElementById('bsaResultValue'); var container = document.getElementById('bsaResultContainer'); var infoDiv = document.getElementById('bsaInfo'); var bsa = 0; if (isNaN(weight) || isNaN(height) || weight <= 0 || height <= 0) { alert("Please enter valid positive numbers for height and weight."); return; } if (formula === "mosteller") { // Formula: sqrt( (height * weight) / 3600 ) bsa = Math.sqrt((height * weight) / 3600); infoDiv.innerText = "Calculated using the Mosteller formula."; } else if (formula === "dubois") { // Formula: 0.007184 * weight^0.425 * height^0.725 bsa = 0.007184 * Math.pow(weight, 0.425) * Math.pow(height, 0.725); infoDiv.innerText = "Calculated using the DuBois and DuBois formula."; } else if (formula === "haycock") { // Formula: 0.024265 * weight^0.5378 * height^0.3964 bsa = 0.024265 * Math.pow(weight, 0.5378) * Math.pow(height, 0.3964); infoDiv.innerText = "Calculated using the Haycock formula."; } else if (formula === "gehan") { // Formula: 0.0235 * weight^0.51456 * height^0.42246 bsa = 0.0235 * Math.pow(weight, 0.51456) * Math.pow(height, 0.42246); infoDiv.innerText = "Calculated using the Gehan and George formula."; } resultDiv.innerText = bsa.toFixed(2) + " m²"; container.style.display = "block"; }

What is Body Surface Area (BSA)?

Body Surface Area (BSA) is the measured or calculated surface area of a human body. In clinical medicine, BSA is often considered a more accurate indicator of metabolic mass than body weight because it is less affected by abnormal adipose tissue (body fat).

Why is BSA Important?

BSA calculations are vital in various medical fields for several critical reasons:

• Dosage Calculation: Many chemotherapy drugs and other high-potency medications are prescribed based on m² rather than weight alone to ensure therapeutic efficacy while minimizing toxicity.
• Cardiac Index: Cardiologists use BSA to normalize cardiac output measurements, providing a more accurate assessment of a patient's heart function relative to their body size.
• Renal Function: The Glomerular Filtration Rate (GFR) is often adjusted to the average adult BSA of 1.73 m².
• Fluid Replacement: Specifically in burn victims, BSA (often estimated via the Rule of Nines) helps determine the volume of fluid resuscitation required.

Common BSA Formulas Explained

There are several mathematical models used to estimate BSA. Our calculator provides the four most clinically validated methods:

1. Mosteller Formula: Published in 1987, this is the most commonly used formula due to its simplicity. It is calculated as the square root of (Height in cm × Weight in kg) divided by 3600.

2. DuBois and DuBois Formula: One of the oldest and most widely cited formulas, developed in 1916. It is particularly popular in metabolic studies.

3. Haycock Formula: Often preferred for pediatric patients (infants and children) because it was developed using a study group that included a wide range of body sizes, from neonates to adults.

Example Calculation

If an adult patient weighs 80 kg and stands 180 cm tall, the Mosteller BSA calculation would be:

Step 1: 80 × 180 = 14,400
Step 2: 14,400 / 3600 = 4
Step 3: Square root of 4 = 2.00 m²

Average BSA Values

While BSA varies significantly based on age and gender, common averages include:

• Neonates (Newborns): 0.25 m²
• Children (9 years): 1.07 m²
• Adult Women: 1.60 m²
• Adult Men: 1.90 m²

Disclaimer: This calculator is for educational purposes only. Clinical decisions should always be made by qualified healthcare professionals using standardized medical equipment and protocols.