Body Surface Area Calculator
Free BSA calculator: compute body surface area from height and weight with the Mosteller, Du Bois, Haycock and Gehan-George formulas, plus the average.
About the Body Surface Area Calculator
Body surface area (BSA) is the estimated total area of the body's skin in square metres, used in medicine to scale drug doses (especially chemotherapy), cardiac index and burn assessment more accurately than weight alone. This free BSA calculator takes just height (cm) and weight (kg) and computes BSA with four standard equations — Mosteller, Du Bois, Haycock and Gehan-George — plus their average.
The Mosteller formula, BSA = √(height × weight ÷ 3600), is highlighted because it is the easiest to verify and the most widely used clinically. A typical adult falls around 1.7 m². Medical, nursing and pharmacy students across Pakistan and India use these formulas in coursework daily. Results appear instantly in your browser; clinical decisions should always be confirmed by a professional.
How to Use the Body Surface Area Calculator
- 1Enter height in centimetres.
- 2Enter weight in kilograms.
- 3Compare BSA across the four formulas and the average.
Frequently Asked Questions
How is BSA calculated with the Mosteller formula?
BSA = √(height × weight ÷ 3600). For 170 cm and 70 kg: √(170 × 70 ÷ 3600) = √3.3056 ≈ 1.82 m². Its simplicity — one multiplication, one division, one square root — is why hospitals adopted it widely.
Why are there several BSA formulas and which should I use?
Each was fitted to different measurement datasets: Du Bois (1916) is the oldest and still common in cardiology; Haycock suits children; Gehan-George used the largest sample. For a 170 cm, 70 kg adult they agree within a few percent (about 1.80-1.82 m²), so Mosteller is a fine default.
What is a normal body surface area?
Average values are roughly 1.9 m² for adult men, 1.6 m² for adult women, and 1.07 m² for a 9-year-old child. The often-quoted 'standard adult' in dosing references is 1.73 m², which is also the normalization constant used for kidney function (eGFR).
Why is BSA used for drug dosing instead of weight?
Metabolic rate, blood volume and organ function track surface area better than raw weight, so mg/m² dosing is more consistent across body sizes. A chemotherapy dose of 100 mg/m² for a patient with BSA 1.82 m² means 182 mg. Dosing decisions must always be made by clinicians.