Body Surface Area Calculator
Calculate BSA using six validated clinical formulas
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About Body Surface Area Calculator
Body Surface Area (BSA) is a measurement of the total surface of the human body, expressed in square meters (m²). It is widely regarded as a more accurate clinical scaling indicator than body weight because metabolic processes — including drug clearance, cardiac output, and renal filtration — correlate more closely with surface area than mass alone.
This calculator implements six validated formulas: Mosteller (1987), the most commonly used due to its simplicity; DuBois & DuBois (1916), the original and longest-standing formula; Haycock (1978), designed for infants and children; Gehan & George (1970), popular in oncology dosing; Boyd (1935), valid across all age groups; and Fujimoto (1968), optimised for Asian populations.
BSA is most commonly used to dose chemotherapy agents, calculate cardiac index (CO/BSA), estimate glomerular filtration rate corrections, and assess burn extent. The formulas typically agree to within 5–10% for adults of average build.
These calculations are clinical reference tools. They are not diagnostic and should not replace professional medical judgment.
How to Use the BSA Calculator
- 1 Select your unit system — Imperial (feet/lbs) or Metric (cm/kg).
- 2 Enter your height. In imperial mode, enter both feet and inches.
- 3 Enter your weight in pounds or kilograms. Results update automatically.
- 4 Review the average BSA (the headline figure) and individual formula outputs in the table.
- 5 For clinical use, choose the formula appropriate to the context — Mosteller for general dosing, Haycock for pediatrics, Fujimoto for Asian populations.
Frequently Asked Questions
Which BSA formula is most accurate?
No formula is universally most accurate — accuracy depends on population and body type. The Mosteller formula is the most widely used in clinical practice because it is simple, easy to memorize, and produces results within 1–3% of more complex formulas for adults of average build. For children, Haycock is preferred. For Asian populations, Fujimoto provides better calibration.
Why is BSA used instead of body weight for drug dosing?
Many physiological processes — including basal metabolic rate, cardiac output, renal blood flow, and chemotherapy clearance — correlate more closely with body surface area than with weight alone. Using BSA reduces inter-individual variability in drug exposure, particularly for narrow-therapeutic-index drugs such as cytotoxic chemotherapy agents.
What is a normal BSA value?
For an average adult man, BSA is approximately 1.9 m². For an average adult woman, it is around 1.6 m². Newborns have a BSA of about 0.25 m², which increases steadily through childhood. The clinical reference value for an "average adult" used in pharmacology is 1.73 m².
How is BSA used in cardiology?
BSA is used to calculate the cardiac index (CI = cardiac output ÷ BSA), which normalizes cardiac output across different body sizes. A normal cardiac index is between 2.5 and 4.0 L/min/m². Stroke volume index, systemic vascular resistance index, and several echocardiographic measurements are also indexed to BSA.
Is BSA dosing always recommended for chemotherapy?
BSA dosing is the long-standing standard for most cytotoxic agents, but it is not perfect. For some drugs (e.g. carboplatin), creatinine-clearance-based dosing such as the Calvert formula is preferred. For highly obese patients, capping BSA at 2.0 m² or using ideal body weight is sometimes practiced to limit toxicity. Always follow the relevant treatment protocol.
Why does the calculator show six different formulas?
Different formulas were developed in different decades, populations, and clinical contexts. Showing all six lets you cross-check results, see how much variation exists for your inputs, and pick the one most appropriate to your use case. For most purposes the formulas agree to within 5–10%.
Does BSA differ between men and women?
Yes — but only because men are on average taller and heavier. The formulas themselves are sex-neutral and rely solely on height and weight. We display sex as a reference label so you can interpret your result against population averages.