Body Surface Area Calculator

Estimate body surface area from height and weight (Mosteller & Du Bois).

Body surface area (Mosteller)

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Du Bois formula

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Height

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Weight

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In sq ft

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A reference estimate used by clinicians for some dosing — not a health rating or diagnosis. For any medical decision, consult a professional.

A measure of body size

Body surface area estimates the total skin area of the body from height and weight. For many physiological purposes it is a better yardstick than weight alone, which is why it appears throughout medicine.

Mosteller: BSA = √(height_cm × weight_kg ÷ 3600)

The calculator shows the simple Mosteller estimate alongside the older Du Bois formula. They typically land within a few percent of each other.

Worked example

For someone 170 cm and 70 kg, the Mosteller formula gives a body surface area of about 1.82 m², with the Du Bois formula very close at around 1.81 m².

How BSA is used

Clinicians scale certain drug doses — chemotherapy is a notable example — and measures like cardiac index to body surface area rather than weight. It is a working reference figure, calculated by professionals as part of care, not a number to interpret as a verdict on health.

Worth remembering

Estimate, not measurement. It is derived from height and weight.
Formulas agree closely. Mosteller and Du Bois rarely differ much.
Leave dosing to clinicians. Use this for reference only.

This is general information, not medical advice.

Frequently asked questions

What is body surface area?

An estimate of the total external area of the body, in square metres. It often tracks physiological measures better than weight alone, which is why clinicians use it.

What are the Mosteller and Du Bois formulas?

Two well-known ways to estimate BSA from height and weight. Mosteller is a simple square-root formula; Du Bois is an older power-law one. They usually agree closely.

Why is BSA used in medicine?

Some drug doses, and measures like cardiac index, are scaled to BSA rather than weight. It is a reference figure used by professionals, not a health rating in itself.

How accurate is it?

These are estimates from height and weight, not direct measurements, so they carry some error. For any clinical decision, rely on a qualified professional, not a web estimate.