Body Surface Area Calculator

BSA is used widely in clinical dosing (especially chemotherapy and pediatric drugs), in cardiac index, and in burn-area estimation. Enter your height and weight in metric or imperial and see all five formulas plus their average. The values usually agree to within a few percent — Mosteller is the most common in clinical practice because of its simple square-root form.

The five formulas disagree because they were fitted to different people. Du Bois and Du Bois, still the most cited, was published in 1916 from measurements of nine subjects, one of them a child with a wasting condition. Boyd, Gehan and George, Haycock and Mosteller each came later from larger or differently selected groups. The spread between them is small in the middle of the range and widens at the extremes, so for a very small child or a patient with obesity the choice of formula changes the number by more than the few percent it changes for an average adult.

The reason clinical dosing uses BSA at all is historical rather than physiological. It entered oncology because early dose-finding work scaled between species by surface area, and it persists because the trials that established the doses were run that way. It is a poor proxy for the things that actually determine drug handling, namely organ function and body composition, which is why several agents have moved to flat dosing or to dosing on renal function instead.

Mosteller's popularity is a matter of arithmetic rather than accuracy. Its form, the square root of height times weight divided by 3600, can be done on any calculator and gives results close to Du Bois across the normal range, which made it the one that spread through wards before everyone had a computer.

The average shown here is a convenience for comparison and is not a clinical value. Any real dose should come from the formula your institution's protocol specifies, since the protocol and the formula were validated together.