Body Surface Area Calculator
Calculate body surface area with the Mosteller formula and compare Du Bois, Haycock and Gehan–George, the equations used for drug dosing and physiology.
The skin area of your body, used for dosing and physiology.
How the body surface area calculator works
Body surface area is estimated from height and weight because it correlates with metabolic rate and blood volume better than weight alone, which is why chemotherapy doses, cardiac index and kidney function are scaled to it. Mosteller's formula (1987) is the simplest — the square root of height × weight ÷ 3,600 — and agrees with the others to within a few percent for adults.
Du Bois (1916) is the classic reference, Haycock (1978) was fitted to infants and children as well as adults, and Gehan–George (1970) came from a large series of direct measurements. Clinicians choose the one their protocol names.
Formula: Mosteller: BSA (m²) = √(height cm × weight kg ÷ 3600)
Worked examples
| Inputs | Body surface area (Mosteller) | Note |
|---|---|---|
| 175 cm, 75 kg | 1.91 m² | √(13,125 ÷ 3,600) |
| 160 cm, 55 kg | 1.56 m² | a smaller adult |
| 6 ft 2 in, 210 lb | 2.23 m² | converted to 188 cm, 95.3 kg |
FAQFrequently asked questions
Why is body surface area used for drug doses?
Because for many drugs clearance tracks metabolic rate and organ size, which scale with surface area more closely than with weight. Chemotherapy protocols are the best-known example.
Which formula do hospitals use?
Mosteller is common because it is easy to compute at the bedside; Du Bois remains the traditional reference in many texts. Protocols usually name the one they validated with.
What is a typical adult BSA?
Around 1.7–2.0 m². A reference value of 1.73 m² is used to normalize kidney function (eGFR).
Does it work for children?
The Haycock formula was fitted across infants to adults and is often preferred in paediatrics; Mosteller is also widely used. Dosing children is a clinical decision, not a calculator's.
Where these figures come from
- Mifflin MD et al., "A new predictive equation for resting energy expenditure in healthy individuals", Am J Clin Nutr 1990 — the BMR equation used here
- World Health Organization — Waist circumference and waist–hip ratio (2008 expert consultation) — waist-to-hip cut-offs
- Tanaka H, Monahan KD, Seals DR, "Age-predicted maximal heart rate revisited", J Am Coll Cardiol 2001 — 208 − 0.7 × age
- Nathan DM et al., "Translating the A1C assay into estimated average glucose values" (ADAG), Diabetes Care 2008 — eAG = 28.7 × A1c − 46.7
- Mosteller RD, "Simplified calculation of body-surface area", N Engl J Med 1987 — BSA = √(height × weight / 3600)
- Centers for Disease Control and Prevention — national health guidance
Last checked: September 2026. The equations are fixed by their published papers and do not change with tax years or regulations; the thresholds quoted in verdicts name the body that set them.