= R. D. Mosteller
{c}
\b[R. D. Mosteller] authored the 1987 letter \i[Simplified calculation of body-surface area], associated with the <Mosteller formula> for estimating <body surface area> from height and <mass>.<Simplified calculation of body-surface area by R. D. Mosteller>[Primary byline; New England Journal of Medicine 317(17), 1098]{ref} The published initial-only identity is retained.
The official VA technical manual records the unit-specific equation
$$
\mathrm{BSA}_{\mathrm{m^2}}=
\sqrt{\frac{h_{\rm cm}m_{\rm kg}}{3600}},
$$
where height is in centimetres and body <mass> in kilograms.<Formulas for Body Surface Area Calculator in the VA Clinical Reminders Manager's Manual>[Printed p.36, Formulas for Body Surface Area Calculator]{ref} It is an empirical estimate of area, not a direct measurement of the skin's complete geometry.
For an original arithmetic example, height 180 cm and <mass> 80 kg give $\sqrt{180\times80/3600}=2$ m$^2$. Entering 1.8 as though metres were the required input would instead give 0.2 m$^2$: a hundredfold change in the numerical height becomes a tenfold change after taking the square root. The unit convention is therefore part of the formula, not an optional label.
A small-error calculation gives
$$
\frac{\delta\mathrm{BSA}}{\mathrm{BSA}}\simeq
\frac12\frac{\delta h}{h}+\frac12\frac{\delta m}{m}.
$$
This describes sensitivity to input errors within the equation; it does not quantify the empirical model's accuracy for a particular person. Area estimates can also enter derived quantities such as <cardiac index>, defined as <cardiac output> divided by <body surface area>. For stipulated output 5 L/min and area 2 m$^2$, that ratio is 2.5 L/(min m$^2$). A normalization changes the stated quantity; it does not create an additional direct flow measurement.
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