Body Surface Area Calculator
Estimate body surface area (BSA) from height and weight using the Mosteller, Du Bois, Haycock, Gehan-George, and Boyd formulas, in metric or imperial. Calculates in your browser.
Body surface area (Mosteller)
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Show the math
The Mosteller formula is the simplest and most widely used:
BSA = √(height × weight ÷ 3600)
The Du Bois, Haycock, Gehan-George, and Boyd formulas use fitted power laws of height and weight. They were each derived from a different study group, so they disagree by a few percent, so treat the spread as a band. This is for information only: it does not calculate medication doses, so never use it to work out a dose.
What this does
A body surface area (BSA) calculator estimates the total area of your skin in square meters from your height and weight. Clinicians use BSA to scale things like cardiac output and some treatments because it tracks body size better than weight alone. This tool is for information only: it does not calculate medication doses, so never use it to work out a dose.
How to use it
- Enter your height and weight.
- Switch between metric and imperial if needed.
- Read the BSA from each formula.
- Use the Mosteller value unless a formula is specified for you.
How it works
The Mosteller formula takes the square root of height (cm) times weight (kg) divided by 3600. The Du Bois, Haycock, Gehan-George, and Boyd formulas use fitted power laws of height and weight and usually agree within a few percent.
BSA = √(height×weight / 3600)
Understanding your result
BSA grows with both height and weight, so taller or heavier people have more and children much less. The formulas differ slightly because each was fitted to a different study group; the Mosteller formula is the most common in clinical practice because it is simple and accurate. The result is for information only, not for working out medication doses.
Example
At 180 cm and 75 kg, the Mosteller BSA is about 1.94 m².
Last updated .
Frequently asked questions
Which BSA formula should I use?
Mosteller is the most widely used because it is simple and accurate. Du Bois is the historical standard. Unless your clinician specifies one, the values are close enough to be interchangeable.
What is a normal body surface area?
It depends on your height and weight: at 180 cm and 75 kg the Mosteller BSA is about 1.94 m², smaller adults are lower, and children much lower.
Can I use this to work out a medicine dose?
No. This tool is not for calculating medication doses. Doses are set by your doctor or pharmacist, who check much more than body size.
Is my data stored?
No. Everything is calculated locally in your browser.
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