Body Surface Area (BSA) Calculator: Mosteller, Du Bois, Haycock and More
Free body surface area (BSA) calculator for adults and children with ten formulas: Mosteller, Du Bois, Haycock, Gehan and George, Boyd and more. See them side by side, how BSA changes with weight, and quick helpers for dose by BSA, cardiac index and GFR.
Mix units freely: kg or lb, cm or ft + in; the twin fields fill in as you type. Works for adults and children.
Compare the formulas
Formulas agree within about 5% for most adults. Clinicians usually use Mosteller (simple and accurate) or Du Bois; paediatric work often uses Haycock or Mosteller.
How BSA changes with weight
Quick clinical calculators
For education only. Never use these numbers to dose a medicine for a real patient without checking with a pharmacist or prescriber and the drug's own protocol.
Dose by BSA
Index a measurement
eGFR ↔ absolute GFR
Child dose from adult dose
What is body surface area (BSA)?
Body surface area is the total area of your skin, in square metres (m²). An average adult has about 1.9 m² (men) or 1.6 m² (women); the standard reference is 1.73 m². Because it tracks metabolic mass better than weight alone, doctors use it to scale chemotherapy and other drug doses, to index cardiac output (cardiac index) and kidney function (GFR) so people of different sizes can be compared, to size burn treatments and to dose children.
BSA formulas
Example (Mosteller): 180 cm and 80 kg gives sqrt(180 × 80 ÷ 3600) = sqrt(4) = 2.00 m².
Questions
- Which formula is the best?
- There is no single winner. Mosteller is the easiest and is the default in most hospitals; Du Bois is the historical standard. They differ by a few percent in normal-sized adults, more at the extremes.
- Why is BSA used for chemotherapy?
- Historically it correlates with blood volume and organ size. Many centres now cap BSA at 2.0 m² for obese patients, as some guidelines recommend; follow your protocol.
- Does it work for children?
- Yes: Mosteller and Haycock are widely used. Costeff's formula uses weight alone and is only for children.
- Is my data private?
- Yes. Everything stays in this browser.
General information, not medical advice. Related: BMI Calculator · Ideal Weight Calculator · Waist-to-Hip Ratio Calculator