Calculate body surface area

Compare four published height-and-weight equations for estimated body surface area in square metres.

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ToolBody Surface Area Calculator
Input
Output
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How it works

Du Bois, Haycock, and Boyd apply different empirical powers to height and weight, whereas Mosteller takes the square root of centimetres times kilograms divided by 3,600. Boyd uniquely converts kilograms to grams before applying its weight-dependent exponent; all four values remain separate because their cohorts and errors differ.

Formula
Mosteller BSA = √(height cm × weight kg ÷ 3,600)
  • No equation is treated as canonical or averaged into a fifth result.
  • Height and weight must both be positive before logarithms, roots, and fractional powers are evaluated.

Worked example

170cm, 70kg adult
The four formulas side by side
Input
											Height cm: 170
Weight kg: 70
Output
												Du bois: 1.81
Mosteller: 1.82
Haycock: 1.83
Boyd: 1.83

When to use this

Oncology protocols express some doses in mg/m², cardiology reports cardiac index in L/min/m², and paediatric or adult clinical records must preserve which named BSA equation a protocol requires.

Edge cases

  • Zero or negative height or weight is rejected before any formula can return a nonphysical or nonfinite area.
  • Infants, very small adults, and large body sizes can widen disagreement between equations, so the four estimates are never silently averaged.
  • Boyd expects weight in grams internally; entering grams in the kilogram field would be scaled by another 1,000 and is therefore a unit error.

References