Body Surface Area Calculator
This calculator computes the total surface area of a human body — its body surface area (BSA). Direct measurement of BSA is difficult, so many estimation formulas have been published; the results below compare eight of the most popular in square meters, square feet, and square inches.
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The following are the body surface area results based on popular formulas:
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(Responsive Fluid)
Table of average BSAs
| ft2 | m2 | |
|---|---|---|
| Newborn child | 2.69 | 0.25 |
| Two-year-old child | 5.38 | 0.5 |
| Ten-year-old child | 12.27 | 1.14 |
| Adult female | 17.22 | 1.6 |
| Adult male | 20.45 | 1.9 |
What BSA is used for
Clinicians often prefer BSA to body weight because it tracks metabolic mass — the body's energy requirement — more accurately. Metabolic mass can be approximated by fat-free mass: everything in the body that is not fat, including bones, tendons, organs, muscle, blood, and nerves. Since fat is not metabolically active, fat-free mass is a reasonable stand-in, and BSA correlates with it. BSA is also used to compute cardiac index, which relates heart performance to body size, and most commonly to set chemotherapy doses. That use is debated: for drugs with a narrow therapeutic index — where the gap between an effective dose and a toxic one is small — BSA may not be accurate enough, and BSA itself loses accuracy at the extremes of height and weight, where BMI can be the better estimate. Even so, BSA-based chemotherapy dosing still produces more consistent effects than dosing by weight alone.
The formulas
The most widely used is the Du Bois formula, shown to be effective for estimating body fat in both obese and non-obese patients, unlike body mass index. In every formula below, BSA is in m2, W is weight in kg, and H is height in cm:
Du Bois formula:
BSA = 0.007184 × W0.425 × H0.725
Du Bois D, Du Bois EF (Jun 1916). "A formula to estimate the approximate surface area if height and weight be known". Archives of Internal Medicine 17 (6): 863-71. PMID 2520314.
Mosteller formula:
BSA = 0.016667 × W0.5 × H0.5
Mosteller RD. "Simplified calculation of body-surface area". N Engl J Med 1987; 317:1098. PMID 3657876.
Haycock formula:
BSA = 0.024265 × W0.5378 × H0.3964
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.
Gehan and George formula:
BSA = 0.0235 × W0.51456 × H0.42246
Gehan EA, George SL. Cancer Chemother Rep 1970, 54:225-235.
Boyd formula:
BSA = 0.03330 × W(0.6157 − 0.0188 × log10(W)) × H0.3
Boyd, Edith (1935). The Growth of the Surface Area of the Human Body. University of Minnesota. The Institute of Child Welfare, Monograph Series, No. x. London: Oxford University Press.
Fujimoto formula:
BSA = 0.00883 × W0.444 × H0.663
Fujimoto S, Watanabe T, Sakamoto A, Yukawa K, Morimoto K. Studies on the physical surface area of Japanese. 18. Calculation formulae in three stages over all ages. Nippon Eiseigaku Zasshi 1968;5:443-50. (The constant also circulates in print as 0.008883; the value 0.00883 is the one that reproduces published Fujimoto results, and is used here.)
Takahira formula:
BSA = 0.007241 × W0.425 × H0.725
Fujimoto S, Watanabe T, Sakamoto A, Yukawa K, Morimoto K. Studies on the physical surface area of Japanese. 18. Calculation formulae in three stages over all ages. Nippon Eiseigaku Zasshi 1968;5:443-50.
Schlich formula:
Women: BSA = 0.000975482 × W0.46 × H1.08
Men: BSA = 0.000579479 × W0.38 × H1.24
Schlich E, Schumm M, Schlich M: "3-D-Body-Scan als anthropometrisches Verfahren zur Bestimmung der spezifischen Körperoberfläche". Ernährungs Umschau 2010;57:178-183.