Body Surface Area Calculator
Calculate Body Surface Area (BSA) in square meters from height and weight using the Du Bois, Mosteller, Haycock, and other standard formulas. BSA is widely used in medicine to dose drugs and to normalize physiological measurements like cardiac output.
How to Use
- Enter your weight in kilograms.
- Enter your height in centimeters.
- Read your BSA in square meters, shown for each standard formula.
- Compare the formulas — the Mosteller equation is the simplest and most widely used clinically; Du Bois is the historical reference.
- Use a preset (adult male, adult female, child, or large adult) to see typical values quickly.
Show Work
Formulas
About the Body Surface Area Calculator
The Body Surface Area Calculator gives you a fast, free answer for health and fitness tracking without sending anything off your device. Calculate Body Surface Area (BSA) in square meters from height and weight using the Du Bois, Mosteller, Haycock, and other standard formulas. BSA is widely used in medicine to dose drugs and to normalize physiological measurements like cardiac output.
How it works
Enter your figures and the result appears instantly, updating the moment you change anything. There is no submit button and nothing to wait for, so it is easy to try a few what-if numbers and compare the results. Just check each box holds the kind of value it expects.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
What is Body Surface Area used for?
BSA is used in medicine to scale dosing and physiological values to body size. Chemotherapy and some other drugs are dosed in milligrams per square meter of BSA. It is also used to compute the cardiac index (cardiac output divided by BSA) and to normalize measures like glomerular filtration rate. The average adult BSA is roughly 1.7 m².
Which BSA formula should I use?
The Mosteller formula — the square root of (height in cm × weight in kg ÷ 3600) — is the most common in clinical practice because it is simple and accurate across a wide range of sizes. The Du Bois formula (1916) is the historical standard still cited in research. The Haycock formula is often preferred for infants and children. For most adults the formulas agree within a few percent.
Why is BSA used for drug dosing instead of body weight?
BSA correlates more closely than body weight with several physiological variables such as metabolic rate, blood volume, and renal function. For drugs with a narrow therapeutic window — chemotherapy in particular — dosing per square meter helps deliver a more consistent exposure across patients of different sizes, though the practice is debated and increasingly supplemented by other methods.
Does BSA change with body composition?
The standard formulas use only height and weight, so they do not distinguish muscle from fat. Two people of the same height and weight get the same BSA regardless of build. The formulas were derived from direct measurements on a limited number of subjects, so they are best treated as good approximations rather than exact figures.
Can I rely on this for medical decisions?
This calculator is informational and educational only — it is not medical advice. Drug dosing and clinical decisions must be made by a qualified clinician using validated tools and the full clinical picture. If a BSA figure matters for your care, confirm it with your healthcare provider.
How do I use the Body Surface Area Calculator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Does it cost anything or need an account?
No. The tool is completely free, there is no account to create, and it keeps working offline after the page first loads.
Is anything I type uploaded?
No. The tool works entirely on your device, so the values you enter never leave your browser.
Common Use Cases
Understanding a chemotherapy dose
See how a per-square-meter dose translates to a total amount for a given body size.
Calculating cardiac index
Normalize cardiac output to BSA, the standard way to compare it across body sizes.
Pediatric reference
Use the Haycock formula, designed to remain accurate for children and infants.
Comparing standard formulas
See how Du Bois, Mosteller, and Haycock differ for the same height and weight.
Physiology and nursing study
A quick reference for students learning how body size is scaled in clinical formulas.
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