Estimate your body surface area (BSA) in square meters from height and weight, using the Mosteller formula by default. Compare Du Bois, Haycock, and Gehan-George for additional context. This is an estimate, not a direct measurement.
Figures are estimates for general informational use, based on established BSA formulas. This calculator does not diagnose any condition and does not provide medication dosing — BSA-based clinical decisions should be made by a qualified healthcare professional.
Body surface area (BSA) is an estimate of the total external surface area of the human body, usually expressed in square meters (m²). It is commonly estimated from height and weight using formulas such as Mosteller, Du Bois, Haycock, and Gehan-George.
The Mosteller formula is BSA = √[(height in cm × weight in kg) / 3600]. It's the default here because of its simplicity and wide use; Du Bois, Haycock, and Gehan-George are available for comparison.
No. BSA estimates surface area in m², while BMI relates weight to height as a screening measure expressed in kg/m². They answer different questions.
No. BSA is used in some clinical dosing protocols, but the actual dose is a decision made by a qualified healthcare professional using the applicable drug-specific protocol — not something to calculate and apply yourself.
Body surface area is an estimate of how much external surface the human body has, related to overall body size. It is commonly derived from height and weight, expressed in square meters, and used in a range of clinical and scientific calculations. This calculator does not physically measure your skin surface — it applies a mathematical formula to your entered height and weight.
Directly measuring total body surface area is cumbersome and impractical outside specialized research settings. Mathematical formulas instead provide practical estimates using easily obtained variables — height and weight. Over the past century, researchers have produced many such equations; more than 40 BSA formulas have been developed in total, though only a handful remain in common use.
Published by Mosteller in 1987 as a simplified BSA calculation, this formula is popular because it's simple, easy to calculate, and widely recognized across clinical settings. It's the default formula used by this calculator.
One of the earliest and most historically established BSA equations. It remains a common reference point in the literature — it isn't obsolete, and it isn't universally superior to newer formulas either.
Developed using data that included infants, children, and adults, the Haycock formula is often used when pediatric BSA estimation matters, though it can be applied across body sizes.
An established alternative equation, reported alongside Mosteller, Du Bois, and Haycock in the scientific literature as one of the commonly referenced BSA formulas.
| Formula | Equation | Typical use / context |
|---|---|---|
| Mosteller | √[(h × w) / 3600] | Simple, widely used clinical estimation |
| Du Bois and Du Bois | 0.007184 × h0.725 × w0.425 | Historical / long-established reference |
| Haycock | 0.024265 × h0.3964 × w0.5378 | Pediatric and general BSA estimation |
| Gehan and George | 0.0235 × h0.42246 × w0.51456 | Established alternative equation |
Different equations can produce slightly different BSA estimates for the same height and weight. No formula is labeled "most accurate" here — formula performance can vary by population, body size, and clinical context, and published research has found that disagreement among formulas can become meaningful in some circumstances (for example, at higher body weights). Disagreement between formulas doesn't automatically mean one of them is wrong.
This is an example calculation, not a medical recommendation.
Illustrative example only — not guidance for a specific child's clinical care.
For a typical adult body size, the four formulas agree closely — differences become more noticeable at extremes of height or weight.
BSA is expressed as an area, in square meters (m²) — not to be confused with meters (m), a length unit. For reference, 1 m² equals 10,000 cm². To convert a result from this calculator to cm², multiply the m² value by 10,000.
| BSA | BMI |
|---|---|
| Body surface area | Body mass index |
| Estimates surface area from height and weight | Relates weight to height |
| Usually expressed in m² | Expressed in kg/m² |
| Used in some clinical calculations (dosing, indexing) | Common general screening measure |
| Not associated with defined health categories | Adult BMI has defined screening categories |
BSA and BMI answer completely different questions. See the BMI Calculator for weight-relative-to-height screening categories.
Weight is a measure of mass; BSA is an estimated area. Two people with the same weight can have different BSA if their height differs, since height is a separate input in every BSA formula.
BSA is not a body-fat measurement. It does not directly determine body-fat percentage, lean mass, or muscle mass. For those, see the Body Fat Calculator, Lean Body Mass Calculator, and FFMI Calculator.
BSA has been used in some medication dosing contexts, including chemotherapy, and in other physiological indexing applications in clinical practice. This section explains those relationships at a general level — it does not calculate a personal dose.
Medication dosing based on BSA is a clinical decision and should be determined by the treating healthcare professional and the applicable prescribing protocol. This calculator does not tell you what dose of any medication to take.
Some oncology regimens have historically used body-surface-area-based dosing. However, drug-specific protocols differ, dose caps may apply, renal and hepatic function may matter, and age and clinical condition are also considered. This page does not provide chemotherapy dose calculations.
Cardiac index is commonly expressed as cardiac output divided by BSA:
This explains the mathematical relationship only — it is not an interpretation of any individual's cardiac function.
Some renal measurements are normalized to a standard BSA, often 1.73 m², as a way of comparing results across people of different sizes. BSA itself does not measure kidney function — kidney-function estimation is a separate calculation. See the GFR Calculator for that specific topic.
Burn assessment uses the percentage of total body surface area (%TBSA) affected, which is a different concept from calculating a person's total BSA in m². This calculator does not include a burn-area estimator.
Yes, BSA equations can be applied to children, but formula performance can vary with age and body size. The Haycock formula was specifically developed from measurements that included infants, children, and adults, which is why it's often referenced for pediatric use. This calculator does not use BSA results to suggest medication decisions for children — for pediatric medical decisions, consult a qualified healthcare professional.
Pediatric BSA estimation, and infant estimation in particular, can be especially sensitive to formula selection and measurement accuracy. No formula is claimed here to be universally accurate for all infants — if a clinical protocol specifies a particular equation, that protocol should be followed.
Yes — both height and weight influence every BSA formula. That said, BSA equations may behave somewhat differently across body-size extremes; published research has identified differences among formulas in overweight and obese populations. This page does not offer a separate "obesity formula."
There is no single universal accuracy figure for a BSA calculator. Accuracy depends on the formula used, the population it was derived from, how precisely height and weight were measured, body size, body proportions, and the reference method the formula was originally validated against. Different BSA equations can and do produce different values for the same person, and a published review comparing many formulas found that differences can become clinically meaningful in some circumstances. This page does not claim a specific accuracy percentage or describe any BSA figure as exact.
This calculator estimates BSA. Direct measurement of whole-body surface area requires specialized methodology well beyond a web calculator and isn't the normal consumer approach — so an estimated BSA is not the same thing as a directly measured surface area.
Small errors in height or weight entry can shift the calculated BSA. Measuring height accurately and using a reliable scale, rather than entering rounded or remembered figures, will generally produce a more consistent estimate.
Same height and weight, run through different BSA equations, can produce slightly different results — that's expected, not an error. It reflects the different reference populations and mathematical assumptions behind each formula, not one calculation being "wrong."
This page does not present an "ideal," "healthy," or "normal" BSA target. BSA naturally varies with body size, and there is no authoritative universal target to measure yourself against. An "average" adult BSA is sometimes loosely cited around 1.7–2.0 m², but that's a rough population reference, not a personal goal.
BSA is not a diagnosis. It does not independently diagnose obesity, being underweight, heart disease, kidney disease, cancer, diabetes, or any other metabolic condition.
BSA is estimated using established published formulas. Mosteller (the default) is BSA = √[(height(cm) × weight(kg))/3600]. Optional formulas — Du Bois and Du Bois, Haycock, and Gehan and George — use the coefficients shown in the Formulas section above. Results are calculated from unrounded intermediate values and displayed to two decimal places (e.g., 1.87 m²) to avoid false precision.
Authoritative references to verify before publishing:
Author: the CalculatorSearch team. Add a "Reviewed By" credit only once a genuinely qualified medical or clinical professional has checked this content — do not publish the placeholder byline above as a real reviewer. Content last reviewed: September 2026.
This calculator performs its computation in your browser. No account is required, and the tool does not store your height or weight beyond what's needed to display your result on this page.