Body Surface Area Calculator

Written byOleh Soloninupdated 29 August 2026

Height, cm

Weight, kg

Result

Mosteller, m²1.909
Du Bois, m²1.903
Haycock, m²1.917
Gehan-George, m²1.921
Mean of the four, m²1.912
Spread between them, m²0.018

This result is informational only and is not professional advice.

Several formulas, and they disagree

Works out body surface area with four equations at once — Mosteller, Du Bois, Haycock and Gehan-George — and shows the spread between them.

Body surface area is used where height and weight alone will not do: chemotherapy dosing, cardiac index, burn assessment. It cannot be measured directly, so empirical equations stand in for it.

There are more than a dozen of them and they give slightly different answers. Mosteller took hold in clinical practice for its simplicity — the square root of height times weight over 3600. Du Bois is older and does better on average builds; Haycock suits children.

What this calculator shows

Body surface area by four equations at once
The mean and the spread between the largest and smallest estimate
How much the choice of equation actually matters

What to keep in mind

Every equation is empirical and derived from a limited sample: at extremes of height and weight they diverge more.
For drug dosing, use whichever equation the protocol or label specifies rather than the one that looks 'more accurate'.

FAQs

Which body surface area formula is most accurate?

For average-build adults all four agree closely. Mosteller is easiest to do in your head, Du Bois is the classic, Haycock is preferred in children.

What is body surface area used for?

Dosing drugs with a narrow therapeutic window, chiefly in oncology, plus normalising cardiac output and estimating burn extent.

What is an average body surface area?

About 1.7 m² for women and 1.9 m² for men. The 1.73 m² that eGFR is normalised to is the average adult figure.

What is the Mosteller formula?

The square root of height in centimetres times weight in kilograms, divided by 3600. It works on any pocket calculator.

Worked example

An average-build adult

Input: 175 cm, 75 kg

Output: 1.909 m² by Mosteller, 1.903 by Du Bois

Note: The spread across four equations here is 0.018 m², under one percent. At very high or very low weights it grows to several percent, and then the choice of equation starts to count.

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Useful links

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