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Body surface area calculator (Mosteller and Du Bois)

Estimate body surface area from height and weight with the Mosteller and Du Bois formulas, and learn where each one came from.

BSA, Mosteller (m²)
BSA, Du Bois (m²)

Formula

BSA=H×W3600\text{BSA} = \sqrt{\frac{H \times W}{3600}}
How it's derived

This calculator is for education. It isn’t medical advice, and dosing decisions belong to a clinician.

The formula

BSAMosteller=H×W3600\text{BSA}_{\text{Mosteller}} = \sqrt{\frac{H \times W}{3600}} BSADu Bois=0.007184×W0.425×H0.725\text{BSA}_{\text{Du Bois}} = 0.007184 \times W^{0.425} \times H^{0.725}

HH is height in centimetres, WW weight in kilograms, and BSA is in square metres.

Where it comes from

Body surface area is used to dose some drugs, especially chemotherapy, and to normalize heart and kidney measurements between people of different sizes. Nobody measures skin directly, so it’s estimated from height and weight.

Du Bois (1916). Delafield and Eugene Du Bois coated subjects in thin moulds of paper and paraffin, then cut the moulds into flat pieces and measured their area. They fitted a power law to just nine people. The exponents 0.425 and 0.725 are the best fit to that data, not values derived from geometry.

Mosteller (1987). Raymond Mosteller wanted something you could do on a calculator. He noticed that a square root of height times weight tracks the established formulas closely. The 3600 is a fitted scaling constant that makes the units come out in m². His one-paragraph letter is now the most widely used BSA formula.

Both are empirical fits. The simple dimensional idea behind them is that surface area grows like a length squared. If you treat the body as a cylinder of fixed density, H⋅W\sqrt{H \cdot W} has that scaling.

Worked example

A person 170 cm tall weighing 70 kg:

BSA=170×703600=3.306=1.82 m2\text{BSA} = \sqrt{\frac{170 \times 70}{3600}} = \sqrt{3.306} = 1.82\ \text{m}^2

Du Bois gives 1.81 m². The average adult is around 1.7 to 1.9 m².

Watch out for

  • Small samples. Du Bois fitted nine people, including no young children and few people with obesity. Formulas can disagree by 10% or more at the extremes.
  • Use the formula your protocol specifies. Hospitals standardize on one so that doses are consistent.

Sources

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