Body Surface Area Calculator
Calculate your Body Surface Area (BSA) in m² using the Mosteller, Haycock, or DuBois formula. Clinicians and pharmacists use BSA to dose chemotherapy, renal drugs, and burn treatments accurately.
About this calculator
Body Surface Area is the total external surface of the human body, measured in square metres, and is widely used in medicine because many physiological processes scale with surface area rather than weight alone. Three formulas are supported. The DuBois formula (default) is: BSA = 0.007184 × weight^0.425 × height^0.725. The Mosteller formula is simpler: BSA = √(weight × height / 3600). The Haycock formula, preferred for paediatric patients, is: BSA = 0.024265 × weight^0.5378 × height^0.3964. In all formulas weight is in kg and height in cm, and the result is in m². The Mosteller formula is popular in clinical practice because it can be calculated mentally or on a basic calculator, while DuBois and Haycock offer greater precision across a wider range of body sizes.
How to use
Example: adult patient, weight = 70 kg, height = 175 cm, using the Mosteller formula. Step 1 — Multiply weight × height: 70 × 175 = 12 250. Step 2 — Divide by 3600: 12 250 / 3600 = 3.4028. Step 3 — Take the square root: √3.4028 ≈ 1.845 m². Now try DuBois for the same patient: 0.007184 × 70^0.425 × 175^0.725. 70^0.425 ≈ 6.107, 175^0.725 ≈ 37.17, so BSA ≈ 0.007184 × 6.107 × 37.17 ≈ 1.631 m². The difference illustrates why the choice of formula matters for drug dosing.
Frequently asked questions
Which body surface area formula should I use for chemotherapy dosing?
The DuBois formula has historically been the standard for chemotherapy dosing and remains the most cited in oncology literature. However, many institutions have shifted toward the Mosteller formula because of its simplicity and comparable accuracy. The Haycock formula is recommended for paediatric oncology patients due to its validation across a wider range of ages and body sizes. Always follow the protocol specified by the prescribing oncologist or institutional guideline, as the chosen formula will determine the calculated dose directly.
How does body surface area differ from BMI and why is it used in medicine?
BMI is a ratio of weight to height squared and is used as a population-level screening index for overweight and obesity, not for drug dosing. BSA, by contrast, estimates the actual physical area of skin covering the body, which correlates strongly with cardiac output, renal filtration rate, and metabolic rate. This makes BSA a more physiologically meaningful scaling factor for drugs that distribute through body compartments or are cleared by organs whose function scales with body size. BMI tells you nothing about how large a person's organ systems are, whereas BSA provides a practical proxy.
What is the normal body surface area for an adult and how does it vary?
The average BSA for an adult male is approximately 1.9 m² and for an adult female approximately 1.6 m², though these values vary considerably with height and weight. A commonly used reference value of 1.73 m² represents the average for a 70 kg, 170 cm adult and appears in many pharmacokinetic equations. Athletes with greater muscle mass or tall individuals may have BSA values exceeding 2.2 m², while small or underweight adults may fall below 1.5 m². Because drug doses are typically calculated per m², even modest differences in BSA can meaningfully change the prescribed dose.