What is body surface area (BSA) used for?

BSA is used primarily in medicine to calculate drug dosages, especially for chemotherapy agents, where dosing by body weight alone is insufficient. Some cardiac measurements (cardiac index, stroke volume index) are normalized per BSA. Burn percentage coverage is also estimated relative to BSA using the Rule of Nines. BSA correlates better than body weight with metabolic rate, organ size, and drug distribution volume.

What is the Mosteller formula for BSA?

Mosteller BSA (m²) = √((height cm × weight kg) / 3600). This is the most commonly used formula due to its simplicity and reasonable accuracy. For a 70 kg, 170 cm person: √(170×70/3600) = √(11900/3600) = √3.306 ≈ 1.818 m². Other formulas include DuBois & DuBois, Haycock, and Gehan & George, each with slightly different coefficients validated in different populations.

What is the average BSA for adults?

The average BSA for adult men is approximately 1.9 m²; for adult women approximately 1.6 m². This varies with height and weight. BSA is relatively stable across healthy adults of normal weight. Pediatric BSA ranges from ~0.25 m² for newborns to adult values by late adolescence. In oncology, standard chemotherapy doses are often calculated per 1.73 m² (a reference BSA).

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 × H^0.725 × W^0.425	Adults — historically standard
Haycock (1978)	BSA = 0.024265 × H^0.3964 × W^0.5378	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.

Why Body Surface Area Matters in Medicine

Body surface area (BSA) is essential for drug dosing in oncology and paediatrics. Chemotherapy doses are calculated in mg/m² of BSA rather than mg/kg body weight, because tumour drug sensitivity and organ toxicity both scale with body surface. BSA is also used to calculate cardiac index (cardiac output per m² of BSA), to size prosthetic heart valves, and to estimate burns coverage using the Rule of Nines. Average adult BSA is approximately 1.7 m² for women and 1.9 m² for men.

BSA Formulas Compared

Formula	Best used for
DuBois & DuBois (1916)	General clinical use
Mosteller (1987)	Simplest, widely used — √(H × W / 3600)
Haycock (1978)	Paediatric patients
Gehan & George (1970)	Chemotherapy dosing

BSA in Clinical Medicine

Body Surface Area (BSA) is used in medicine because many physiological measurements scale better with body surface than with weight alone. Chemotherapy dosing uses BSA because anticancer drugs have a narrow therapeutic window — too little and they're ineffective; too much and they're toxic. The Mosteller formula (most widely used today) calculates BSA as the square root of (height in cm × weight in kg / 3600). The DuBois formula, published in 1916, is BSA = 0.007184 × height^0.725 × weight^0.425. Haycock's formula is preferred for paediatric patients because it performs better at extremes of body size.

A typical adult BSA is 1.7–1.9 m². The average male is approximately 1.9 m² and the average female 1.6 m². Burn patients are assessed using the Rule of Nines, which divides the body into regions each representing 9% of BSA — critical for calculating fluid resuscitation volumes.

BSA Formula Comparison

Formula	Equation	Best For
Mosteller	sqrt(height(cm) × weight(kg) / 3600)	General adults
DuBois	0.007184 × H^0.725 × W^0.425	Historical standard
Haycock	0.024265 × H^0.3964 × W^0.5378	Paediatrics
Boyd	0.0003207 × H^0.3 × W^(0.7285 − 0.0188 log W)	Neonates
Gehan-George	0.0235 × H^0.42246 × W^0.51456	Widely cited