What is body surface area?

An estimate of the total external area of the body, in square metres, from your height and weight.

Why is BSA used in medicine?

Many drug doses (e.g. chemotherapy) and measures like cardiac index are scaled to BSA rather than weight alone.

Du Bois vs Mosteller — which is more accurate?

They agree within a couple of percent for most adults; Mosteller is simpler and the common clinical default.

What is an average body surface area?

Roughly 1.7 m² for adults (about 1.9 m² for men and 1.6 m² for women on average).

How do I calculate BSA by hand?

Mosteller is easiest: take the square root of (height in cm × weight in kg ÷ 3600).

Body Surface Area Calculator

This body surface area calculator estimates your BSA in square metres from height and weight using the Du Bois and Mosteller formulas. BSA is used mainly in clinical settings — for drug dosing, cardiac index, and burn assessment.

What BSA is and why it's used

Body surface area is an estimate of the total external area of the body. In medicine it's often preferred to bodyweight for scaling things that track more closely with surface area than mass — chemotherapy and other drug doses, cardiac index, and the extent of burns. A typical adult sits around 1.7 m².

The formulas

Both take weight in kilograms and height in centimetres:

Du Bois (1916): BSA = 0.007184 · W^0.425 · H^0.725
Mosteller (1987): BSA = √(H · W ÷ 3600)

Worked example

For a 70 kg adult who is 170 cm tall: Mosteller = √(170 × 70 ÷ 3600) = √3.31 ≈ 1.82 m², and Du Bois ≈ 1.81 m² — a difference of well under 1%.

Which formula to use

Mosteller is the simplest and is the common clinical default — you can compute it on any calculator. Du Bois is the historical reference the others are validated against. For most adults they differ by only a couple of percent, so either is fine; this tool shows both.

Frequently asked questions

What is body surface area?: An estimate of the total external area of the body, in square metres, from your height and weight.
Why is BSA used in medicine?: Many drug doses (e.g. chemotherapy) and measures like cardiac index are scaled to BSA rather than weight alone.
Du Bois vs Mosteller — which is more accurate?: They agree within a couple of percent for most adults; Mosteller is simpler and the common clinical default.
What is an average body surface area?: Roughly 1.7 m² for adults (about 1.9 m² for men and 1.6 m² for women on average).
How do I calculate BSA by hand?: Mosteller is easiest: take the square root of (height in cm × weight in kg ÷ 3600).

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Disclaimer. These BSA estimates are for general information and education only and are not a substitute for clinical dosing decisions or professional medical advice.