Body Surface Area (BSA) Calculator

What body surface area estimates

Body surface area (BSA) is an estimate of the body’s external area, reported here in square meters (m²). This calculator accepts height and weight in either metric or US customary units and displays five estimates side by side: Du Bois, Mosteller, Haycock, Gehan–George, and Boyd. The Du Bois estimate is also shown as the headline value. The formulas are empirical estimates and can return different results from the same measurements.

Five equations, different estimates

The Mosteller equation is BSA = √(height in cm × weight in kg ÷ 3600). The calculator also applies these equations:

• Du Bois: 0.007184 × weight^0.425 × height^0.725
• Haycock: 0.024265 × weight^0.5378 × height^0.3964
• Gehan–George: 0.0235 × weight^0.51456 × height^0.42246
• Boyd: 0.0003207 × height^0.3 × (weight in grams)^(0.7285 − 0.0188 × log10(weight in grams))

In these formulas, height is in centimeters and weight is in kilograms except where Boyd explicitly uses grams. The WHO Model Formulary for Children reproduces a Mosteller-based equation in its discussion of medicines whose monographs express doses by BSA. That context does not make a calculator result a dosing instruction.

For a reproducible comparison, height 170 cm and weight 65 kg produce approximate BSA results of 1.76 m² by Du Bois, 1.75 m² by Mosteller, 1.77 m² by Haycock, 1.76 m² by Gehan–George, and 1.73 m² by Boyd. Display rounding is to two decimal places.

Enter measurements and compare the estimates

1. Select units first

   Choose Metric to enter height in centimeters and weight in kilograms, or US customary units to enter height in inches and weight in pounds. Switching unit systems clears both fields so a value is not accidentally reinterpreted in the other unit.

2. Enter positive measurements

   Type height and weight. Results appear when both values are greater than zero. The customary-unit values are converted to centimeters and kilograms before the formulas are evaluated.

3. Read the formula comparison

   The large result is Du Bois; the comparison list shows the other four estimates. Use the same input pair when comparing formulas. The copy control beside the primary result copies the displayed two-decimal value with m².

4. Clear before another person or case

   Use Reset to clear both measurements. You can also share a result link containing the entered unit system and measurements; check that those values are appropriate before sharing.

Questions about formula choice and units

Clinical use requires the applicable protocol

This calculator provides mathematical estimates for information and comparison. It does not diagnose a condition, recommend treatment, or calculate a medicine dose.

• Use the formula and measurement conventions specified by the treating clinician or protocol. Do not assume the primary Du Bois value is the correct value for every application.
• Height and weight alone cannot establish an appropriate dose. Do not start, stop, or change treatment based on this result.
• Check units carefully. The tool converts inches and pounds to metric units before applying the equations; an incorrect unit selection changes the result.
• Formula estimates can be less representative for people outside the populations or circumstances for which a formula is appropriate. Seek qualified clinical guidance for individual interpretation.