Body Surface Area Calculator: Mosteller and Du Bois

How to use this body surface area calculator

Choose Metric (kilograms and centimetres) or Imperial (pounds, feet and inches).
Enter your weight and height.
Read the large figure: the Mosteller estimate of your body surface area, with Du Bois and Haycock alongside.
Use it as the size measure it is — never as a way to work out a medicine dose.

What body surface area is used for

Body surface area (BSA) estimates the total area of your skin from your height and weight. It sounds like a curiosity, but clinicians use it as a size yardstick: some drug doses, burn assessments, cardiac measurements and kidney-function numbers are scaled to BSA because it tracks metabolic size better than weight alone.

This page does the arithmetic only. It shows the three standard formulas — Mosteller as the headline, with Du Bois and Haycock alongside — and it never turns the result into a medicine dose. Dosing belongs to the prescribing clinician, who weighs far more than one number.

The formulas

Mosteller (1987)

√(height in cm × weight in kg ÷ 3,600)

The modern default in most hospitals: one square root, easy to compute, and as accurate as the older formulas in validation studies.

Du Bois (1916)

0.007184 × kg^0.425 × cm^0.725

The original formula, fitted to just nine subjects measured with paper moulds — still widely quoted after a century.

Haycock (1978)

0.024265 × kg^0.5378 × cm^0.3964

Fitted across infants, children and adults, so it behaves better at the small end of the size range.

Examples

Person	Weight	Height	Surface area
Adult, 80 kg, 178 cm	80 kg	178 cm	1.99 m²
Adult, 65 kg, 165 cm	65 kg	165 cm	1.73 m²
Adult, 95 kg, 185 cm	95 kg	185 cm	2.21 m²

Three mistakes people make with body surface area

Using BSA to dose medicine yourself

Some clinical doses are scaled to BSA, but the actual prescription also depends on the drug, the condition, organ function and the clinician's judgment. Never convert this number into a dose on your own.

Expecting the formulas to match exactly

Mosteller, Du Bois and Haycock were fitted to different people a century apart. A difference of 0.01 or 0.02 m² between them is normal and changes nothing in practice.

Confusing BSA with BMI

BMI is a weight-for-height ratio used to screen weight categories. BSA is an area — how much skin you have. They answer different questions and are not interchangeable.

Frequently asked questions

What is body surface area?

An estimate of the total area of your skin, in square metres, calculated from your height and weight. For a typical adult it comes out somewhere between about 1.6 and 2.0 m² — roughly the area of a large door.

Should I use Mosteller or Du Bois?

Either. Mosteller is the modern hospital default because it is a single square root and validates just as well; Du Bois is the century-old original and is still quoted everywhere. On the same body they rarely differ by more than 0.02 m².

What is an average body surface area?

Reference tables often quote about 1.7 m² for an average adult woman and 1.9 m² for an average adult man, but the honest range is wide — height and weight move it a lot, and there is no healthy or unhealthy BSA by itself.

Why do doctors use body surface area?

Because it scales with metabolic size better than weight alone. Some chemotherapy and other drug doses, burn-size assessments, cardiac index and kidney-function estimates are expressed per square metre of BSA.

Can I use this result to work out a medicine dose?

No. This page only does the surface-area arithmetic. Where a dose is BSA-based, the prescribing clinician sets it using the drug, your condition and your organ function as well. Never dose medicine from a calculator.

How is BSA different from BMI?

BMI divides weight by height squared to screen weight categories. BSA estimates an area — the size of your skin. One is a screening ratio, the other is a physical size measure used for scaling clinical quantities.

Privacy and important information

This calculator runs entirely in your browser: your numbers are never sent to a server, stored, or shared. Body surface area here is a calculation only — it is not medical advice, and it must never be used to set a medicine dose.

Part of RahaKit's free health calculators.

Body Surface Area Calculator