Body Surface Area Formula | BSA Calculation Methods Explained
Compare all major body surface area formulas including Mosteller, DuBois, Haycock, Gehan-George, and Boyd with worked examples and accuracy comparisons. Free calculator.
What Is Body Surface Area (BSA)?
Body surface area (BSA) is a measurement of the total surface area of the human body, expressed in square meters (m²). Unlike body weight, BSA correlates more closely with organ size and metabolic rate, making it the preferred reference value for dosing many chemotherapy agents, calculating cardiac index, and setting fluid replacement targets in burn patients.
Major BSA Formulas Compared
| Formula | Year | Equation | Best Used For |
|---|---|---|---|
| DuBois & DuBois | 1916 | 0.007184 × H0.725 × W0.425 | Adults; most widely cited in oncology |
| Mosteller | 1987 | √(H × W / 3600) | Adults & pediatrics; simplest, widely recommended |
| Haycock | 1978 | 0.024265 × H0.3964 × W0.5378 | Pediatric patients; most validated in children |
| Gehan & George | 1970 | 0.0235 × H0.42246 × W0.51456 | Children and small adults |
| Boyd | 1935 | 0.0003207 × H0.3 × W(0.7285 − 0.0188 × log W) | Extremely large or small patients |
H = height in centimeters; W = weight in kilograms for all formulas above.
Worked Example: 170 cm, 70 kg Adult
| Formula | BSA Result (m²) | Difference from Mosteller |
|---|---|---|
| DuBois | 1.799 m² | −0.01 m² |
| Mosteller | 1.809 m² | — |
| Haycock | 1.836 m² | +0.027 m² |
| Gehan & George | 1.824 m² | +0.015 m² |
| Boyd | 1.837 m² | +0.028 m² |
Which Formula Should You Use?
For adult oncology drug dosing, the DuBois formula remains the most commonly cited in pharmacological literature, so it is used by default in most hospital protocols. However, multiple oncology societies now recognize Mosteller as the preferred formula due to its simplicity and comparable accuracy. For children under 18, Haycock is generally recommended. Always follow the specific protocol of the medication or clinical guideline being applied.
Frequently Asked Questions
Why is BSA used instead of body weight for drug dosing?
BSA scales more consistently with glomerular filtration rate (how fast the kidneys clear drugs), cardiac output, and metabolic rate than body weight alone. This makes it a better predictor of drug clearance and toxicity thresholds for agents like chemotherapy, where the therapeutic window is narrow.
Is BSA used in metric or imperial units?
All standard BSA formulas use metric units — height in centimeters and weight in kilograms. If you have height in inches and weight in pounds, convert first: 1 inch = 2.54 cm, 1 lb = 0.4536 kg.