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# Body surface area

In physiology and medicine, the body surface area (BSA) is the measured or calculated surface of a human body. For many clinical purposes BSA is a better indicator of metabolic mass than body weight because it is less affected by abnormal adipose mass. Estimation of BSA is simpler than many measures of volume.

## Uses

Examples of uses of the BSA:

## Calculation

Various calculations have been published to arrive at the BSA without direct measurement, starting in 1916 with the Dubois & Dubois formula. A commonly used formula is the Mosteller formula, published in 1987:

Metric (area in square metres from weight in kilograms and height in centimetres): ${x}= \sqrt\frac{\mbox{weight} \times \mbox{height} }{3600}$

half-English units (area in square metres from weight in pounds, height in inches): ${x}= \sqrt\frac{\mbox{weight} \times \mbox{height} }{3131}$

Another is the Haycock formula (in children): ${x}=0.024265 \times {weight \mbox{ (kg)}}^{0.5378} \times {height \mbox{ (cm)}}^{0.3964}$,

Du Bois & Du Bois, Arch Intern Med 1916;17:863: ${x}=(71.84 \times {weight \mbox{ (kg)}}^{0.425} \times {height \mbox{ (cm)}}^{0.725})/10000$,

Gehan EA, George SL, Cancer Chemother Rep 1970;54:225-235: $\mathrm{S} = 0.0235 \times height \mbox{ (cm)}^{0.42246} \times weight \mbox{ (kg)}^{0.51456}$ ,

Boyd's Formula: $\mathrm{S} = 0.0003207 \times height \mbox{ (cm)}^{0.3} \times weight \mbox{ (g)}^{(0.7285 - 0.0188 \log_{10}{weight \mathrm{ (g)}})}$.

## Normal values

• "Normal" BSA is generally taken to be 1.7 m².
• Average BSA for men: 1.9 m²
• Average BSA for women: 1.6 m²
• Average BSA for child (9 years): 1.07 m²
• Average BSA for child (10 years): 1.14 m²
• Average BSA for child (12-13 years): 1.33 m²
• Average BSA for neonate: 0.25 m2
• Average BSA for 2 year old child: 0.5 m2

## References

• Mosteller RD. Simplified calculation of body-surface area. N Engl J Med 1987;317:1098. PMID 3657876.
• Haycock GB, Schwartz GJ, Wisotsky DH Geometric method for measuring body surface area: A height-weight formula validated in infants, children and adults J Pediatr 1978;93:62-66