Body Surface Area Calculator
Calculate body surface area using the Du Bois, Mosteller and Haycock formulas.
Please note: For general information only. This is not medical advice — speak to a doctor or registered dietitian before changing your diet, training or medication.
What the Body Surface Area Calculator does
Body surface area correlates better with metabolic rate and blood volume than weight alone, which is why it drives drug dosing in oncology and paediatrics. Several formulas exist and generally agree within a few percent.
Formula
Mosteller: √((height cm × weight kg) ÷ 3600)Du Bois: 0.007184 × height^0.725 × weight^0.425Haycock: 0.024265 × height^0.3964 × weight^0.5378
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Units | one of 2 options | Yes | — |
| Weight | kg or lb | Yes | Accepts 1 or more. |
| Height | cm or ft + in | Yes | Accepts 1 or more. |
How to use it
- Choose Units.
- Enter Weight and Height.
- Select Calculate.
Worked example
An adult 175 cm tall weighing 70 kg.
- Height
- 175 cm
- Weight
- 70 kg
√((175 × 70) ÷ 3600) = 1.845 m² by Mosteller.
Reading the result
- Body surface area tracks metabolic rate and blood volume better than weight alone, which is why chemotherapy and paediatric doses are calculated from it.
- A typical adult falls between about 1.6 and 2.0 m². The common formulas usually agree within a few percent of each other.
Assumptions and limitations
- Every formula here is an estimate from height and weight, validated on general populations. Accuracy falls at the extremes of body size, including in infants and in severe obesity.
Common mistakes
- Mixing unit systems between height and weight, which produces a plausible-looking but wrong figure.
- Using a BSA estimate to set an actual dose. Dosing is a clinical decision that accounts for organ function and the specific drug.
Frequently asked questions
What is a typical adult BSA?
About 1.7 m² for an average adult woman and 1.9 m² for an average adult man.
Method and sources
Method. Three published BSA formulas computed side by side — Mosteller as the headline, with Du Bois and Haycock alongside so the spread between them is visible.
Assumptions
- Height and weight are the only inputs; every BSA formula infers surface area from those two numbers alone.
- The formulas were derived from measured populations and are applied here without adjustment for body shape.
Limitations
- The formulas disagree with each other, typically by a few percent, and none is definitively correct. Where BSA drives a dose, the formula your clinical protocol specifies is the one that matters — not whichever number looks reasonable.
- Accuracy falls at the extremes of body size, including severe obesity and very low weight, where the source populations had few observations.
- This is a calculation, not a clinical decision. Chemotherapy and paediatric dosing are governed by protocol, not by a web page.
Sources
- A formula to estimate the approximate surface area if height and weight be known — Archives of Internal Medicine 17:863–871 (D. Du Bois and E.F. Du Bois), 1916. The Du Bois formula.
- Simplified calculation of body-surface area — The New England Journal of Medicine 317(17):1098 (R.D. Mosteller), 1987. The Mosteller formula used for the headline figure.