Body Surface Area (BSA) Calculator

Body surface area (BSA) is an estimate of the total external area of the body, expressed in square meters (m²). These equations use height in centimeters and weight in kilograms. They estimate total area; they do not measure how much skin is burned or affected by another condition.

The result is educational. Clinical uses of BSA, including any treatment or medicine calculation, require the relevant clinical protocol and professional judgment; this calculator does not recommend a dose or treatment.

Enter positive height and weight values. Each formula returns an estimate in m²:

• Du Bois and Du Bois (1916): 0.007184 × height⁰·⁷²⁵ × weight⁰·⁴²⁵. See the original paper.
• Mosteller (1987): √(height × weight ÷ 3600). See the original letter.
• Haycock, Schwartz, and Wisotsky (1978): 0.024265 × height⁰·³⁹⁶⁴ × weight⁰·⁵³⁷⁸. Their study included 81 people from premature infants to adults.
• Fujimoto and colleagues (1968): 0.008883 × height⁰·⁶⁶³ × weight⁰·⁴⁴⁴. This is the authors' general equation for their Japanese sample aged 6 years and older, not their separate equations for younger children.

For example, at 170 cm and 70 kg, the estimates are 1.81 m² (Du Bois), 1.82 m² (Mosteller), 1.83 m² (Haycock), and 1.76 m² (Fujimoto), rounded to two decimals. The equations can disagree even when given the same inputs.

The displayed values are alternative estimates of the same quantity: total body surface area. They are not percentages, and adding them together has no meaning. For a comparison over time, use the same equation and updated measurements rather than treating a difference between formulas as a change in the body.

A burn-area percentage describes the affected portion of the body and needs its own assessment, such as the methods described by the American Burn Association. This calculator has no information about injury location or extent, so it cannot produce that percentage.

Each equation was fitted to measured bodies in a particular sample. Height and weight alone cannot capture every difference in shape or body composition, and the four results are estimates rather than direct measurements. The source studies do not establish one formula as universally best for every person.

In particular, the Fujimoto equation shown here came from the authors' age-six-and-older group. If an estimate is needed for clinical care, the treating team should select the formula and apply its own protocol. Do not use this page to set or change medicine doses.