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Body Surface Area (BSA) Calculator

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

Your Estimated Body Surface Area:

0.00 m²

(Using Mosteller Formula)

What is Body Surface Area (BSA)?

Body Surface Area (BSA) is 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 because it is less affected by abnormal adipose (fat) tissue. It is a critical metric used by healthcare professionals to calculate dosages for specialized medications, particularly in oncology (chemotherapy) and cardiology.

Why is BSA Calculation Important?

Using weight alone to determine drug dosages can lead to under-dosing or over-dosing, as metabolic rates often scale more closely with surface area than total mass. Key applications include:

• Pharmacology: Determining the therapeutic window for drugs with narrow safety margins.
• Renal Function: Normalizing the Glomerular Filtration Rate (GFR) to assess kidney health.
• Cardiac Index: Relates the cardiac output from the left ventricle in one minute to the body surface area.
• Burn Assessment: Estimating the percentage of the body affected by burns.

BSA Calculation Formulas

This calculator primarily utilizes the Mosteller Formula, which is the most widely used simplified formula in clinical practice today. However, several other validated formulas exist:

Formula Name	Equation (Metric)
Mosteller	√([Height(cm) × Weight(kg)] / 3600)
DuBois & DuBois	0.007184 × Weight(kg)^0.425 × Height(cm)^0.725
Haycock	0.024265 × Weight(kg)^0.5378 × Height(cm)^0.3964

Realistic BSA Examples

The "average" adult is often considered to have a BSA of 1.73 m², which is the standard used to normalize many medical measurements.

• Average Adult Man: Approximately 1.9 m² (e.g., 180cm, 80kg)
• Average Adult Woman: Approximately 1.6 m² (e.g., 165cm, 60kg)
• 9-Year-Old Child: Approximately 1.07 m²

Disclaimer: This calculator is for educational purposes only. Clinical decisions should be made by qualified medical professionals.

function updateLabels() { var unit = document.getElementById('bsa_unit').value; var weightLabel = document.getElementById('weight_label'); var heightLabel = document.getElementById('height_label'); var weightInput = document.getElementById('bsa_weight'); var heightInput = document.getElementById('bsa_height'); if (unit === 'metric') { weightLabel.innerText = 'Weight (kg)'; heightLabel.innerText = 'Height (cm)'; weightInput.placeholder = 'e.g. 70'; heightInput.placeholder = 'e.g. 175'; } else { weightLabel.innerText = 'Weight (lb)'; heightLabel.innerText = 'Height (in)'; weightInput.placeholder = 'e.g. 154'; heightInput.placeholder = 'e.g. 69'; } } function calculateBSA() { var unit = document.getElementById('bsa_unit').value; var w = parseFloat(document.getElementById('bsa_weight').value); var h = parseFloat(document.getElementById('bsa_height').value); var resultContainer = document.getElementById('bsa_result_container'); var resultValue = document.getElementById('bsa_value'); if (isNaN(w) || isNaN(h) || w <= 0 || h <= 0) { alert('Please enter valid positive numbers for weight and height.'); return; } var bsa = 0; if (unit === 'metric') { // Mosteller Formula Metric: sqrt( (cm * kg) / 3600 ) bsa = Math.sqrt((h * w) / 3600); } else { // Mosteller Formula Imperial: sqrt( (in * lbs) / 3131 ) bsa = Math.sqrt((h * w) / 3131); } resultValue.innerText = bsa.toFixed(2) + ' m²'; resultContainer.style.display = 'block'; // Smooth scroll to result resultContainer.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }