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Body Surface Area Calculator
Body surface area by the five published formulas.
Body Surface Area Calculator tool
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Body surface area
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Mosteller
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Du Bois
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Spread across formulas
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BMI for comparison
| Formula | Published | BSA (m²) |
|---|
BSA is used clinically for drug dosing, particularly in chemotherapy, and for indexing cardiac output. The formulas were derived from small samples decades apart and disagree by a few per cent, which is why a prescriber specifies which one to use.
About the Body Surface Area Calculator
Body Surface Area Calculator gives BSA in square metres by the five formulas in clinical use. Mosteller is the simplest -- the square root of height times weight over 3,600 -- and is the one most commonly specified because it is easy to verify by hand, which matters when a dose depends on it.
BSA is used rather than weight for two main purposes: dosing drugs with narrow therapeutic windows, chemotherapy agents in particular, and indexing physiological measurements such as cardiac output so they can be compared between people of different sizes.
The formulas disagree by a few per cent, and the spread is shown for that reason. Du Bois dates from 1916 and was derived from nine subjects; Mosteller from 1987. On a dose calculated per square metre, a few per cent can matter, which is why a prescribing protocol names the formula rather than leaving the choice to whoever does the arithmetic. This calculator is a check on that arithmetic, not a substitute for the protocol.
This is general information and not medical advice. The formula cannot know your medical history, your medication, your body composition or anything else specific to you. Speak to a doctor or another qualified professional about any question concerning your health, and never delay seeking advice because of a figure on this page.
Your measurements are processed inside your own browser. Height, weight, age and anything else you enter never leave your device, nothing is logged, and nothing survives closing the tab.
How to use the Body Surface Area Calculator
- Choose highlightThe fields below change to match what you pick, so only the figures that matter to your case are asked for.
- Enter height (cm) and weight (kg)Decimals are fine, and thousands separators are accepted and ignored.
- Read the body surface area, mosteller and du boisThe figures update as you type. The Calculate button is there if you would rather press something, but nothing waits for it.
- Copy or check the resultCopy the summary with the copy button, or open the table to check it row by row.
Features
- Shows body surface area, mosteller, du bois, spread across formulas and bmi for comparison together, so you are not running it twice
- A results table you can read across
- Updates as you type, with no button to press and no page reload
- Copy the result in one click
- Free, no sign-up, and it runs entirely in your browser
Who uses this tool
The body surface area calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:
- Checking a BSA figure used for a dose calculation
- Comparing the published BSA formulas
- Indexing a physiological measurement by body size
- Getting BSA alongside BMI for a clinical note
Frequently asked questions
Which BSA formula is standard?
Mosteller is the most commonly specified, partly because it can be checked by hand. Du Bois is still widely used. A protocol should state which.
Why use BSA rather than weight for dosing?
Because metabolic rate and organ function scale closer to surface area than to mass. It is an imperfect proxy, and for some drugs flat or weight-based dosing is now preferred.
Is this suitable for children?
The formulas extend to children, and Haycock was derived partly from paediatric data. Paediatric dosing should always follow a specialist protocol rather than a general calculator.
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Checked and rebuilt on 2026-10-14. The method this calculator uses is described in the section above, and corrections go through the contact page.