What is a normal BSA for an adult?

Most adults fall between about 1.6 and 1.9 m², with 1.7 m² often used as a reference average. It rises with both height and weight.

Is BSA the same as BMI?

No. BMI compares weight to height to screen for weight status, while BSA estimates external surface area for scaling doses and physiological measures.

Which BSA formula is best?

Mosteller is favoured for its simplicity and Du Bois for its long clinical history; for most adults they agree closely. Follow whichever your care team specifies.

Can I use BSA to dose my own medicine?

No. BSA-based dosing is a clinical decision made by professionals using verified data; never adjust medication doses yourself.

What Is Body Surface Area (BSA)?

Published 3/6/2026 · 2 min read · Health calculators

Sofia Nunes — Health & wellness writer at Allin

Nutrition · Hydration

Checked against 2 sources

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In short

Body surface area (BSA) is an estimate of the total external area of your body, expressed in square metres. A typical adult has a BSA of about 1.7 m². Clinicians use it to scale drug doses — especially in chemotherapy — and other measurements more accurately than body weight alone, because it tracks the body's metabolic size well.

A doctor speaking with a patient at a hospital bedside. — RDNE Stock project · Pexels · Pexels

Body surface area estimates your body's external area in square metres. Here is how it is calculated and why clinicians use it to dose medicines.

What BSA measures

Body surface area is the total area of the outer surface of the body. You cannot measure it directly, so it is estimated from height and weight using validated formulas. The result is given in square metres (m²), the same unit in every country, and a typical adult sits around 1.6–1.9 m².

Mosteller and Du Bois formulas

Several equations exist. The Mosteller formula is the most popular because it is simple: BSA (m²) equals the square root of height in centimetres times weight in kilograms, divided by 3,600. The older Du Bois formula is also widely used and gives very similar results for most adults. Calculators handle the arithmetic for you.

Why clinicians use it

BSA scales better than weight for many biological quantities. Chemotherapy doses are commonly expressed per square metre, so a patient's BSA sets the dose. It is also used to index cardiac output and kidney function, and to estimate burn extent. Because small errors in dosing matter, the formula and inputs used should always follow the treating team's protocol.

Worked with our own calculator

Body surface area calculator

Given

Weight (kg): 63
Height (cm): 158

Result

Body surface area (m²): 1.663
Du Bois (m²): 1.641
Haycock (m²): 1.676
Gehan & George (m²): 1.682
Boyd (m²): 1.694

These figures are produced by the calculator below, not typed in by hand — they are recomputed whenever the tool changes.

Run it on your own figures →

Frequently asked questions

What is a normal BSA for an adult?: Most adults fall between about 1.6 and 1.9 m², with 1.7 m² often used as a reference average. It rises with both height and weight.
Is BSA the same as BMI?: No. BMI compares weight to height to screen for weight status, while BSA estimates external surface area for scaling doses and physiological measures.
Which BSA formula is best?: Mosteller is favoured for its simplicity and Du Bois for its long clinical history; for most adults they agree closely. Follow whichever your care team specifies.
Can I use BSA to dose my own medicine?: No. BSA-based dosing is a clinical decision made by professionals using verified data; never adjust medication doses yourself.

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For general information only — not medical advice; consult a professional.

Sources

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