BSA Calculator – Body Surface Area

Written by Great Medico

Updated September 24, 2026 •2 min read

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Body measurements become more useful when the formula behind them is easy to see. BSA Calculator – Body Surface Area turns its specific inputs into one focused estimate.

What this calculator does

Body surface area, or BSA, is used in many clinical formulas because it scales body size differently from weight alone. This calculator estimates BSA from height and weight with several established equations. Anthropometric equations are convenient because they use simple measurements, but they describe body size or proportion rather than directly measuring tissue composition or health.

How to use it

Enter or select Height and Weight. Use the units offered by the calculator and keep measurements consistent when you plan to compare results over time.

How the calculation works

The main result uses the Du Bois formula. The calculator also shows estimates from Mosteller, Haycock, Gehan and George, and Fujimoto, each combining height and weight with different constants and exponents.

Example

For the sample values prefilled in this calculator, the primary result is 1.848 m² (Body surface area (Du Bois)), Du Bois is 1.848 m², and Mosteller is 1.845 m². This example is there to show how the inputs flow through the implemented equation; replace the sample values with your own measurements before using the result.

How to interpret the result

BSA is reported in square meters. Slight differences between formulas are expected; a protocol should use the specific BSA equation it names rather than switching formulas casually.

Limitations and notes

BSA is still an estimate derived from body measurements. It should not be used by itself to choose medication doses or treatment settings, and very small or very large body sizes may produce larger differences between equations. For repeat measurements, consistency usually matters more than false precision: use the same unit system, the same tape or scale when possible, and the same anatomical landmarks. A small change near a category boundary should be viewed in context rather than treated as a sudden biological change.