Body Surface Area Calculator
Estimate body surface area (BSA) from height and weight with the Mosteller, Du Bois and Haycock equations. The calculator keeps the methods separate so you can follow the formula named by a clinical or research protocol.
Do not use this page to choose or change a medication dose. BSA formulas are estimates and can disagree. A clinician, pharmacist or protocol must determine whether BSA is appropriate, which equation to use, whether a cap applies and how any dose is rounded.
BSA formulas used
- Mosteller: BSA = √(height cm × weight kg ÷ 3600).
- Du Bois and Du Bois: BSA = 0.007184 × height cm^0.725 × weight kg^0.425.
- Haycock: BSA = 0.024265 × height cm^0.3964 × weight kg^0.5378.
Each result is in square metres (m²). The page does not average the equations because an average is not a substitute for the method required by a protocol.
Four checked examples
| Height and weight | Mosteller | Du Bois | Haycock |
|---|---|---|---|
| 170 cm, 70 kg | 1.8181 m² | 1.8097 m² | 1.8257 m² |
| 180 cm, 80 kg | 2.0000 m² | 1.9964 m² | 2.0066 m² |
| 100 cm, 20 kg | 0.7454 m² | 0.7233 m² | 0.7542 m² |
| 50 cm, 3 kg | 0.2041 m² | 0.1954 m² | 0.2066 m² |
How to use the result safely
- Confirm the current height and weight, the units and the equation required by the source that asked for BSA.
- Do not interchange equations silently. The difference is small for many typical adult measurements but can be more material at body-size extremes.
- Do not infer a “normal” or “healthy” BSA from the result. BSA is a size estimate, not a diagnosis or health score.
- Pediatric, neonatal, oncology, renal, cardiac and research protocols can impose their own equation, rounding, measurement and capping rules.
- If BSA affects treatment, dosing or a medical decision, use the official protocol and have the result independently verified.
Primary sources
- Mosteller RD (1987), Simplified calculation of body-surface area, DOI 10.1056/NEJM198710223171717.
- Du Bois D and Du Bois EF (1916), A formula to estimate the approximate surface area if height and weight be known.
- Haycock GB, Schwartz GJ and Wisotsky DH (1978), Geometric method for measuring body surface area, DOI 10.1016/S0022-3476(78)80601-5.
Related calculators: BMI Calculator, Body Fat Calculator, Calorie Calculator and Percentage Calculator.
Questions
Which BSA formula should I use?
Use the equation specified by the clinical, laboratory or research protocol. If none is specified, ask the responsible professional rather than choosing based only on the largest or smallest result.
Why do the three answers differ?
They were derived with different datasets and mathematical fits. Height and weight are proxies for a three-dimensional body surface, so no equation directly measures the surface.
Can this calculate a chemotherapy or medicine dose?
No. It intentionally stops at BSA. Drug selection, dose, capping, organ-function adjustment and rounding require a current protocol and qualified clinical review.
Does it work for children?
The calculator accepts small measurements and shows the Haycock equation, whose source included infants and children. That does not replace a pediatric protocol, age-appropriate measurement or clinician verification.