Body Surface Area Calculator
Estimate body surface area with Mosteller, Du Bois, Haycock and Gehan-George formulas using height and weight.
Enter your values
Change any assumption and calculate again to compare results.
What body surface area is
Body surface area, or BSA, is an estimate of the external surface area of the body expressed in square metres. It is used in some clinical contexts because it scales differently from body weight alone.
The Mosteller formula is simple and widely used: take height in centimetres multiplied by weight in kilograms, divide by 3,600 and take the square root. This calculator also shows Du Bois, Haycock and Gehan-George estimates so you can see how formulas differ.
Why multiple formulas exist
BSA cannot be measured easily in routine practice, so formulas were developed from different datasets. Most adults will see similar values, but the difference can be larger at extreme body sizes or in children.
If BSA is being used for medication dosing, chemotherapy, cardiac measurements or another clinical decision, use the exact formula required by the clinician or protocol rather than choosing based on convenience.
Unit conversion
You can enter kilograms and centimetres or pounds and inches. The calculator converts to metric internally because the published equations use kilograms and centimetres.
The result is informational. Do not change a prescription or treatment dose based on a website calculation without professional confirmation.
Important information
This calculator is for general education and planning. It is not a diagnosis, medical device or substitute for individualized healthcare advice. Measurements and formula estimates can differ from clinical assessments.
If the result could affect treatment, pregnancy care, medication, driving, military status or another safety-sensitive decision, confirm it with the appropriate qualified professional or official process.
Frequently Asked Questions
Which BSA formula is most common?
Mosteller is widely used because it is simple, but clinical protocols may specify another equation.
Why are the formula results different?
Each formula was fitted to different data and uses different exponents for height and weight.
Can this calculate drug doses?
No. It estimates BSA only. Medication dosing should follow a clinician or protocol.