Body Surface Area Calculator

How to use

1. 1Pick metric (cm, kg) or imperial (ft, in, lb) at the top. Use Switch to convert your current values to the other system without losing them.
2. 2Enter your height and weight, or click a sample chip such as Reference adult (1.73 m^2 target) to preload typical values.
3. 3Read the headline Mosteller result in m^2 and ft^2. The five other formulas appear below for comparison along with the six-formula average.
4. 4Open a per-formula card to see the exact equation used and a one-line note on when that formula is preferred.
5. 5Click Copy summary to grab a plain-text breakdown with all six results, or Copy on any row to copy that single value.

About this tool

Body Surface Area Calculator computes BSA in square meters from your height and weight using six established clinical formulas at once: Mosteller (1987), Du Bois (1916), Haycock (1978), Boyd (1935), Gehan-George (1970), and Fujimoto (1968). Mosteller is the clinical standard for oncology chemotherapy dosing because the square-root form is easy to verify by hand and matches measured BSA closely across adults and children, so the headline result uses Mosteller and the other five are shown for comparison. Inputs accept both metric (centimeters and kilograms) and imperial (feet, inches, and pounds) units, with a one-click switch that converts the current values rather than discarding them. Quick sample chips cover an average adult man, an average adult woman, a reference 1.73 m² adult used for indexing renal function, a school-age child, and an infant, so you can see how BSA scales across the human size range. Each formula card shows the result in m² and ft², the underlying equation with the actual numbers used, and a short note explaining when that formula is preferred. The average across all six formulas is shown alongside Mosteller as a sensitivity check. Two indexed reference values are computed at the resulting BSA: a typical resting cardiac output (cardiac index 3 L/min/m²) and the standard reference indexed GFR of 90 mL/min/1.73 m², so you can see how BSA is used to convert population averages into a per-person estimate. Useful for medical students, nurses, EMS, pharmacists, and oncology professionals checking dosing reference values, and for any health context where weight alone is the wrong scaling factor. All math runs locally on your device using standard JavaScript number operations; your height and weight are not uploaded.

Free to use. Works in your browser. No signup, no login.