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Medical Body Surface Area (BSA) Calculator

Metric (kg / cm) Imperial (lb / in)

Mosteller (Standard) Du Bois Haycock (Best for Children) Gehan & George

Result: 0.00 m²

function toggleUnits() { var system = document.getElementById("unitSystem").value; var wLabel = document.getElementById("weightLabel"); var hLabel = document.getElementById("heightLabel"); if (system === "imperial") { wLabel.innerText = "Weight (lb)"; hLabel.innerText = "Height (in)"; } else { wLabel.innerText = "Weight (kg)"; hLabel.innerText = "Height (cm)"; } } function calculateBSA() { var system = document.getElementById("unitSystem").value; var formula = document.getElementById("formula").value; var wRaw = parseFloat(document.getElementById("weightInput").value); var hRaw = parseFloat(document.getElementById("heightInput").value); if (isNaN(wRaw) || isNaN(hRaw) || wRaw <= 0 || hRaw <= 0) { alert("Please enter valid weight and height values."); return; } var w, h; if (system === "imperial") { w = wRaw * 0.453592; // lb to kg h = hRaw * 2.54; // in to cm } else { w = wRaw; h = hRaw; } var result = 0; var formulaText = ""; if (formula === "mosteller") { result = Math.sqrt((h * w) / 3600); formulaText = "Formula: √( [Height(cm) x Weight(kg)] / 3600 )"; } else if (formula === "dubois") { result = 0.007184 * Math.pow(w, 0.425) * Math.pow(h, 0.725); formulaText = "Formula: 0.007184 x W^0.425 x H^0.725"; } else if (formula === "haycock") { result = 0.024265 * Math.pow(w, 0.5378) * Math.pow(h, 0.3964); formulaText = "Formula: 0.024265 x W^0.5378 x H^0.3964"; } else if (formula === "gehan") { result = 0.0235 * Math.pow(w, 0.51456) * Math.pow(h, 0.42246); formulaText = "Formula: 0.0235 x W^0.51456 x H^0.42246"; } document.getElementById("bsaValue").innerText = result.toFixed(3); document.getElementById("formulaUsed").innerText = formulaText; document.getElementById("resultArea").style.display = "block"; }

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What is Body Surface Area (BSA)?

Body Surface Area (BSA) is a measure of the total 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 (fat) tissue.

Why is BSA Important in Medicine?

Calculating BSA is critical for several medical applications, including:

• Chemotherapy Dosing: Most cytotoxic drugs are dosed based on BSA to ensure therapeutic efficacy while minimizing toxicity.
• Pharmacokinetics: Determining the clearance rates of medications excreted through the kidneys.
• Burn Management: Estimating the extent of body surface affected by burns to guide fluid resuscitation.
• Cardiac Index: Relating cardiac output to the size of the individual.

Common BSA Formulas Explained

While many formulas exist, the Mosteller Formula is the most widely used in clinical settings due to its simplicity. However, the Haycock Formula is often preferred for pediatric patients (infants and children), while the Du Bois Formula is the oldest and historically most referenced.

Calculation Examples:

Example 1: Average Adult
Weight: 70 kg, Height: 175 cm
Using Mosteller: √((175 * 70) / 3600) = 1.84 m²

Example 2: Small Child
Weight: 15 kg, Height: 100 cm
Using Haycock: 0.024265 * 15^0.5378 * 100^0.3964 = 0.64 m²

Frequently Asked Questions

What is a "normal" BSA?
The average BSA for an adult man is generally considered to be 1.9 m², and for an adult woman, it is approximately 1.6 m².

Is BSA better than BMI?
They serve different purposes. BMI (Body Mass Index) identifies weight categories (underweight/obese), whereas BSA is primarily used for precise medication dosing and physiological measurements.

Which formula should I use?
The Mosteller formula is recommended by most pharmacy guidelines for its accuracy and ease of calculation. If you are calculating for a neonate or infant, the Haycock formula is typically the clinical standard.