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Compute BSA (Mosteller, Du Bois, Haycock) used for clinical drug dosing.
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Body Surface Area Calculator delivers exactly what its name promises, compute bsa (mosteller, du bois, haycock) used for clinical drug dosing, fast and free. Because it belongs to ToolsMonk's medical tools collection, the whole workflow happens on a single page instead of being spread across separate apps or websites.
Common scenarios include you want to understand a chemotherapy dose quoted in mg per square metre, you are checking a cardiac index, which is cardiac output divided by bsa, and you want to compare the formulas rather than trust a single unlabelled number. The browser-based design means you can switch devices mid-task and pick up right where you left off, whether it's a one-time job or part of a daily workflow.
Body Surface Area Calculator is designed for people who want a practical, privacy-friendly workflow with instant results inside the larger ToolsMonk library.
| Price | Free, no signup, no paywall, no watermark |
|---|---|
| Works on | Any modern browser: desktop, tablet, and mobile |
| Processing | In your browser, files never leave your device |
| Account required | None |
| Category | Medical Tools |
Choose metric or imperial and enter height and weight
The five formulas compute at once, with Mosteller shown as the headline figure
Compare the spread: on a typical adult they agree within a few percent, and a large disagreement means an input error
Save the result to keep a record as weight changes
Computes body surface area with five published formulas: Mosteller, Du Bois, Haycock, Gehan-George and Boyd
Mosteller is highlighted as the clinical default because it is the simplest and the most widely used
Shows all five together so you can see how closely they agree, which is the practical accuracy check
Works in metric or imperial and saves results so BSA can be tracked as weight changes
You want to understand a chemotherapy dose quoted in mg per square metre
You are checking a cardiac index, which is cardiac output divided by BSA
You want to compare the formulas rather than trust a single unlabelled number
You are tracking BSA over time because weight has changed
Body Surface Area Calculator exists to make one job effortless: compute bsa (mosteller, du bois, haycock) used for clinical drug dosing. Professionals, students, and one-time visitors all get the same instant, accurate results in the browser: no installation, no account, no waiting.
Privacy and portability drive the design: all processing runs locally in your browser, so your files and data never leave your device. It behaves identically in every modern browser, from a desktop workstation to a phone.
Body surface area is the total external area of the body, expressed in square metres. It cannot be measured directly in practice, so it is estimated from height and weight. Every formula here is a regression fitted to a set of people whose surface area was measured by other means, which is why several exist and why they do not agree exactly.
Du Bois and Du Bois published the first widely used formula in 1916, fitted on nine subjects. Mosteller's 1987 simplification, the square root of height times weight over 3600, is now the clinical default because it is trivially checkable by hand and tracks Du Bois closely across adult sizes. Haycock (1978) and Gehan-George (1970) included children in their derivation, which is why they are often chosen in paediatrics.
The reason BSA matters clinically is dosing. Chemotherapy is conventionally prescribed in milligrams per square metre because surface area tracks cardiac output, blood volume and renal filtration better than body weight does. Cardiac index, the number used to compare cardiac output between people of different sizes, is also BSA-normalised, as is the eGFR standard of 1.73 square metres.
The convention is not beyond criticism. BSA-based dosing produces wide variation in drug exposure between patients, and it behaves poorly at the extremes of body size, which is why many protocols cap the value used for very large patients. It persists because decades of dosing evidence were built on it.
This calculator runs entirely in your browser and saves nothing to a server. It reports what the published formulas produce for the height and weight you enter. It is an educational tool, not a dosing tool, and any actual dose is a clinical decision.
Use Mosteller unless you have a specific reason not to: it is the clinical default and the easiest to verify by hand
If one formula disagrees with the others by more than a few percent, check your height and weight units before trusting any of them
For infants and children, Haycock and Gehan-George were fitted with paediatric data and are often preferred
BSA moves with weight, so a figure from six months ago may no longer be the right input
Common questions about this tool, its workflow, and what to expect before you use it.
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Compute BSA (Mosteller, Du Bois, Haycock) used for clinical drug dosing.
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