Body surface area calculator (BSA)
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Result
For exam practice. Doses based on BSA must follow the protocol, which states the formula to use. Never use this result for a real dose.
Calculate the body surface area (BSA) in square metres from height and weight. The Mosteller formula is the default; the DuBois and DuBois and Haycock formulas are shown alongside, so you can see how much they differ. Heights and weights in inches and pounds are converted for you, and each formula is worked out with your numbers.
Step-by-step solution
Mosteller
Other formulas
Key formulas
- Mosteller
- BSA = √(height (cm) × weight (kg) / 3600)
- DuBois and DuBois
- BSA = 0.007184 × weight0.425 × height0.725
- Haycock
- BSA = 0.024265 × weight0.5378 × height0.3964
- Dose by BSA
- dose = dose per m² × BSA
How to calculate body surface area
- Use the height in centimetres and the weight in kilograms. Convert inches with × 2.54 and pounds with × 0.4536.
- Mosteller: BSA = √(height × weight / 3600).
- DuBois and DuBois: BSA = 0.007184 × weight^0.425 × height^0.725.
- Haycock: BSA = 0.024265 × weight^0.5378 × height^0.3964.
- Round as the protocol asks, usually to two decimals. A typical adult has a BSA of about 1.7 to 2.0 m².
Questions and answers
Which BSA formula should I use?
Mosteller is the most widely used because it is simple and accurate for adults. DuBois and DuBois is the classic formula, and Haycock was developed for infants and children. Use the formula that your protocol or exam question names.
How much do the formulas differ?
For average adults the results are usually within about 2%. The differences grow for very small, very large or obese patients.
What is BSA used for?
Dosing of chemotherapy and some other drugs, cardiac index (cardiac output divided by BSA), and normalising kidney function to 1.73 m².
Why does the Mosteller formula divide by 3600?
It comes from fitting measured surface areas: BSA in m² equals the square root of height in cm times weight in kg, divided by 3600. With inches and pounds the constant is 3131 instead.
Is BSA dosing always capped?
Some protocols cap the BSA, often at 2.0 m², and others use the actual value. Always follow the protocol; this calculator is for practice.
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