Body Surface Area Calculator
Body Surface Area — Guide & Formulas
Body Surface Area (BSA) is the measured or calculated surface area of a human body. It is used in clinical medicine to calculate drug doses (particularly chemotherapy), estimate burn area, and assess metabolic rate.
BSA formulas
| Formula | Equation | Best used for |
|---|---|---|
| Mosteller (1987) | BSA = √(H × W / 3600) | Adults — simplest, most widely used |
| DuBois & DuBois (1916) | BSA = 0.007184 × H0.725 × W0.425 | Adults — historically standard |
| Haycock (1978) | BSA = 0.024265 × H0.3964 × W0.5378 | Paediatric patients |
Where H = height in cm, W = weight in kg.
Clinical uses of BSA
- Chemotherapy dosing: most cytotoxic agents are dosed in mg/m² of BSA
- Renal function: GFR is normalised to 1.73 m² (average adult BSA)
- Cardiac output indexing: cardiac index = cardiac output / BSA
- Burn assessment: Rule of Nines uses body regions as percentages of total BSA
- Paediatric dosing: BSA-based dosing is more accurate than weight-based for children
Chemotherapy dose example
If a drug is dosed at 100 mg/m² and the patient's BSA is 1.8 m², the dose = 100 × 1.8 = 180 mg. Always consult your oncology team for actual dosing calculations.
Rule of Nines (burn surface area)
- Head and neck: 9%
- Each arm: 9%
- Chest (front): 9%, Abdomen (front): 9%
- Upper back: 9%, Lower back: 9%
- Each thigh: 9%, each lower leg: 9%
- Genitalia: 1%
References
- Mosteller RD (1987). "Simplified calculation of body-surface area." NEJM 317(17):1098.
- DuBois D, DuBois EF (1916). "A formula to estimate the approximate surface area if height and weight be known." Arch Intern Med 17:863–871.
- Haycock GB et al. (1978). "Geometric method for measuring body surface area." J Pediatr 93(1):62–66.
