Body Surface Area Calculator

Enter your height and weight to estimate body surface area (BSA) in square metres. The calculator shows four validated medical formulas — Mosteller, Du Bois, Haycock and Gehan-George — and highlights the common Mosteller result.

Enter height and weight, then press Calculate BSA.

Body surface area formulas

Body surface area (BSA) is the total area of the outside of the body, in square metres. It can't be measured directly, so clinicians estimate it from height and weight. The most widely used is the simple Mosteller formula:

BSA (m²) = √( height(cm) × weight(kg) ÷ 3600 )

The calculator also reports the older Du Bois, the pediatric-friendly Haycock, and the Gehan-George formulas, which all agree closely for typical adults but diverge a little at the extremes of size.

Worked example

Height 178 cm, weight 75 kg, by Mosteller:

Product: 178 × 75 = 13,350.
Divide: 13,350 ÷ 3,600 = 3.708.
Square root: √3.708 ≈ 1.93 m².

Why BSA matters

BSA scales better than body weight for many physiological measures, so it's used to dose chemotherapy and other drugs, to index cardiac output and kidney function, and to estimate burn coverage. A typical adult is around 1.7 m². Because the formulas are estimates from population data, results can differ by a few percent between methods — the calculator shows them side by side so you can see the spread. This tool is for education; clinical dosing must use the formula and value a clinician specifies.

Tip: looking at body composition instead? See the BMI calculator and the body fat calculator.

Frequently asked questions

Which BSA formula should I use?

Mosteller is the most common because it's simple and accurate across ages, and it's what many hospitals use for drug dosing. Du Bois is the historical standard. They agree within a few percent for typical adults, so the choice rarely changes the answer much.

What is a normal body surface area?

An average adult is roughly 1.7 m², with men a little higher and women a little lower. Children have much smaller BSA — a newborn is around 0.25 m² — which is why pediatric dosing relies on it.

Why is BSA used for drug dosing?

Many drugs distribute and clear in proportion to body size more closely than to weight alone. BSA captures both height and weight, so dosing per square metre gives more consistent blood levels, especially for chemotherapy.

Is this calculator suitable for medical use?

It's for education and quick estimates. For real clinical decisions, use the specific formula your institution mandates and have a qualified professional verify the value — never self-dose from an online estimate.

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Mustafa Bilgic · Editor, Calcool
Implements the Mosteller, Du Bois, Haycock and Gehan-George BSA formulas. Educational, not medical advice. Everything runs in your browser — nothing you enter is uploaded, logged or stored.

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