How do I calculate body surface area?

You need height and weight. The calculator uses the Mosteller formula: BSA = √(height × weight / 3600) and shows the result in m², plus the Du Bois estimate.

What is a normal adult BSA?

On average about 1.7 m²: men usually ~1.9 m², women ~1.6 m². The exact value depends on height and weight — use the calculator.

Mainly for chemotherapy dosing (dose per m²), as well as the cardiac index on echocardiography and normalising some values. In paediatrics, for dosing.

How is Mosteller different from Du Bois?

They are two formulas for the same value. Mosteller is simpler (a square root), Du Bois is the historical first and slightly more complex. Values are close; clinically Mosteller is used more often.

Body surface area calculator (BSA)

Body surface area (BSA) is a value derived from height and weight. It is used to dose chemotherapy, compute the cardiac index on echocardiography and normalise clearances. Enter your height and weight — the calculator returns BSA by the Mosteller formula and shows the Du Bois estimate alongside.

Calculate body surface area

Enter height and weight — the body surface area appears instantly.

Average body surface area

Approximate average BSA values. Your individual result depends on height and weight — use the calculator above.

Group	Average BSA, m²
Adult man	≈ 1.9 m²
Adult woman	≈ 1.6 m²
Child ~9 y	≈ 1.07 m²
Newborn	≈ 0.25 m²

What body surface area is

Body surface area (BSA) is an estimate of a person’s total skin area in square metres. It is hard to measure directly, so it is calculated from height and weight. In adults BSA is usually 1.5–2.0 m².

BSA reflects body size for many physiological calculations better than weight alone: it tracks metabolism, blood volume and organ workload.

Mosteller and Du Bois formulas

The calculator uses the Mosteller formula — the simplest and most common: BSA = √(height[cm] × weight[kg] / 3600). Alongside it shows the classic Du Bois result — the two are close.

Both formulas are estimates. Clinically the Mosteller is usually used for its simplicity and good accuracy.

Why BSA is used

Its main use is chemotherapy dosing: the dose is calculated per m² of body surface. BSA also gives the cardiac index (cardiac output per BSA) on echocardiography and normalises some lab values.

In paediatrics BSA is used for maintenance therapy and dosing where weight is not precise enough.

Limitations

In marked obesity, strict per-BSA dosing is debated: a very large calculated surface can overestimate the dose of toxic drugs. In such cases a doctor adjusts the calculation.

BSA is a helper value, not a health metric: on its own it does not say whether something is “good” or “bad”.

A helper calculation, not a diagnosis

The calculator gives a guide for understanding and preparing for a visit. Drug doses and clinical decisions are made by a doctor considering the whole picture.

Frequently asked questions

You need height and weight. The calculator uses the Mosteller formula: BSA = √(height × weight / 3600) and shows the result in m², plus the Du Bois estimate.
On average about 1.7 m²: men usually ~1.9 m², women ~1.6 m². The exact value depends on height and weight — use the calculator.
Mainly for chemotherapy dosing (dose per m²), as well as the cardiac index on echocardiography and normalising some values. In paediatrics, for dosing.
They are two formulas for the same value. Mosteller is simpler (a square root), Du Bois is the historical first and slightly more complex. Values are close; clinically Mosteller is used more often.
In marked obesity, strict per-BSA dosing is debated — a very large calculated surface can overestimate the dose. A doctor then adjusts it individually.

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This calculator is for reference and information only. Drug doses and clinical calculations are performed by a doctor.