Body Surface Area Calculator
Body surface area (BSA) is a measure of the total external surface area of the human body expressed in square metres. Unlike body weight, BSA correlates well with many physiological parameters including cardiac output, kidney filtration rate, and drug distribution volume. For this reason, BSA is a critical calculation in oncology, where chemotherapy doses are typically prescribed as milligrams per square metre of BSA. It is also used in assessing burns, calculating fluid replacement, and in paediatric medicine where dosing by weight alone can be inaccurate. Two formulas are most widely used clinically. The DuBois formula (1916) was the first validated BSA equation, developed from direct measurements of plaster casts of nine subjects. The Mosteller formula (1987) simplifies the calculation to a square root formula and has been shown to produce comparable accuracy across diverse populations. This calculator shows results from both formulas for direct comparison. Enter your height in centimetres and weight in kilograms.
Formula
Mosteller (1987): BSA = sqrt(height(cm) * weight(kg) / 3600)
DuBois (1916): BSA = 0.007184 * height(cm)^0.725 * weight(kg)^0.425
Result in square metres (m²)
Body Surface Area Calculator: frequently asked questions
What is body surface area used for?
Body surface area (BSA) is used in medicine to calculate doses of chemotherapy drugs, calculate cardiac output index, assess burns (the Rule of Nines), determine fluid replacement needs, and prescribe some other medications where body surface area is a better dosing variable than weight alone. It is also used in clinical research and physiological studies.
Which BSA formula is more accurate?
Both the Mosteller (1987) and DuBois (1916) formulas are widely used clinically. A 1992 study by Verbraecken et al. found that the Mosteller formula had slightly smaller errors across diverse populations. The Mosteller formula is more commonly used in modern clinical practice and oncology protocols because of its simplicity and validated accuracy.
What is a normal BSA for adults?
The average adult BSA is approximately 1.73 m² for men and 1.60 m² for women. Drug dosing protocols sometimes use 1.73 m² as a standardised reference BSA. Individual values vary with body size: a 1.80 m adult weighing 80 kg will have a BSA of approximately 2.0 m².
How is BSA different from BMI?
BSA measures the external surface area of the body in square metres, which is useful for dosing drugs that distribute according to surface area. BMI is a ratio of weight to height squared that approximates body fatness at the population level. BMI does not require knowledge of actual surface area and is used for population health screening rather than individual drug dosing.
Why was BSA originally calculated?
BSA was originally introduced by DuBois and DuBois in 1916 to study basal metabolic rate, which correlates better with surface area than with weight. The finding that many physiological parameters scale with BSA led to its adoption as a dosing variable for drugs with a narrow therapeutic index, particularly cancer chemotherapy agents introduced in the 1950s and 1960s.
Official sources
- Mosteller RD. (1987). "Simplified calculation of body-surface area." New England Journal of Medicine, 317(17):1098.
- DuBois D, DuBois EF. (1916). "A formula to estimate the approximate surface area if height and weight be known." Archives of Internal Medicine, 17(6):863-871.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.