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Body Surface Area (BSA) Calculator

Mosteller Formula (Standard) Du Bois Formula Haycock Formula

Result: 0.00 m²

function calculateBSA() { var w = parseFloat(document.getElementById('weightInput').value); var h = parseFloat(document.getElementById('heightInput').value); var formula = document.getElementById('formulaSelect').value; var result = 0; if (isNaN(w) || isNaN(h) || w <= 0 || h <= 0) { alert("Please enter valid positive numbers for height and weight."); return; } if (formula === "mosteller") { // Formula: sqrt( (H x W) / 3600 ) result = Math.sqrt((h * w) / 3600); } else if (formula === "dubois") { // Formula: 0.007184 * W^0.425 * H^0.725 result = 0.007184 * Math.pow(w, 0.425) * Math.pow(h, 0.725); } else if (formula === "haycock") { // Formula: 0.024265 * W^0.5378 * H^0.3964 result = 0.024265 * Math.pow(w, 0.5378) * Math.pow(h, 0.3964); } var finalBSA = result.toFixed(2); document.getElementById('bsaOutput').innerText = finalBSA; document.getElementById('resultArea').style.display = 'block'; var interpretation = "The average adult body surface area is generally considered to be 1.7 to 1.9 m²."; if (finalBSA 2.2) { interpretation = "This BSA is above the average adult range, typical for taller or larger-framed individuals."; } document.getElementById('interpretationText').innerText = interpretation; }

Understanding 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 alone because it is less affected by abnormal adipose tissue (body fat). This measurement is critical for healthcare professionals, particularly in pharmacology and oncology.

Why is BSA Important in Medicine?

BSA is used primarily for the following medical applications:

• Chemotherapy Dosage: Most chemotherapy drugs are "BSA-dosed" to ensure the patient receives a precise amount of medication relative to their metabolic capacity, minimizing toxicity while maximizing efficacy.
• Renal Clearance: Glomerular Filtration Rate (GFR) is often indexed to BSA (normalized to 1.73 m²) to assess kidney function accurately.
• Cardiac Index: This relates the cardiac output to the patient's size, providing a more relevant metric than simple blood flow volume.
• Fluid Replacement: Especially in burn victims, BSA (specifically the percentage of affected area) guides intravenous fluid resuscitation.

Common BSA Formulas Explained

Because it is difficult to measure skin surface area directly, several mathematical models have been developed over the last century:

1. Mosteller Formula

Created in 1987, this is the most popular formula due to its simplicity. It calculates BSA by taking the square root of (Height in cm × Weight in kg) divided by 3,600. It is the default setting for our calculator above.

2. Du Bois Formula

The Du Bois & Du Bois formula (1916) is the oldest widely used metric. While historically significant, some modern studies suggest it may underestimate BSA in obese patients.

3. Haycock Formula

The Haycock formula is frequently used in pediatrics. It was developed to provide more accurate surface area estimations for infants and small children compared to the Du Bois formula.

BSA Calculation Example

Let's look at a practical example using the Mosteller method:

Patient Profile: Weight = 80 kg, Height = 180 cm.

1. Multiply Height by Weight: 180 × 80 = 14,400.
2. Divide by 3,600: 14,400 / 3,600 = 4.
3. Take the Square Root: √4 = 2.00 m².

In this scenario, a physician would use 2.00 m² to calculate the appropriate dose for medications that require surface area-based scaling.

Disclaimer: This calculator is for educational and informational purposes only. It should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or medication dosage.