# 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:

- Renal function is usually fractioned over the BSA to gain an appreciation of the true required glomerular filtration rate (GFR);
- The Quetelet index uses a somewhat modified form of the BSA;
- The cardiac index is a measure of cardiac output divided by the BSA, giving a better approximation of the required cardiac output;
- Chemotherapy is often dosed according to the patient's BSA.
- Glucocorticoid dosing is also expressed in terms of BSA for calculating maintenance doses or to compare high dose use with maintenance requirement.

## 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):

half-English units (area in **square metres** from weight in pounds, height in inches):

Another is the Haycock formula (in children):

- ,

Du Bois & Du Bois, *Arch Intern Med* 1916;17:863:

- ,

Gehan EA, George SL, *Cancer Chemother Rep* 1970;54:225-235:

- ,

Boyd's Formula:

- .

## 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 m
^{2} - Average BSA for 2 year old child: 0.5 m
^{2}

## 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