Body Surface Area Converter
Our free human metrics converter handles body surface area conversions. See tables, ratios, and examples for quick reference.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator
Body Surface Area Converter
Calculator
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Formula: BSA (DuBois) = 0.007184 x Weight^0.425 x Height^0.725
Worked example โ BSA: 1.8136 m2 | Sample dose (75 mg/m2): 136.0 mg | Cardiac Index: 2.76
Formula
BSA (DuBois) = 0.007184 x Weight^0.425 x Height^0.725
The DuBois formula estimates body surface area using weight in kilograms and height in centimeters raised to fractional powers. The Mosteller formula is simpler: BSA = sqrt(Weight x Height / 3600). The Haycock formula (BSA = 0.024265 x W^0.5378 x H^0.3964) is preferred for pediatric patients. Drug dosing multiplies BSA by the prescribed dose per square meter. Cardiac index = cardiac output / BSA.
Worked Examples
Example 1: Adult BSA Calculation
Problem:Calculate BSA for a patient weighing 70 kg and 170 cm tall using the DuBois formula.
Solution:DuBois: BSA = 0.007184 x 70^0.425 x 170^0.725 70^0.425 = 6.396 170^0.725 = 49.95 BSA = 0.007184 x 6.396 x 49.95 = 1.8136 m2 Mosteller check: sqrt((70 x 170) / 3600) = sqrt(3.306) = 1.8182 m2 Drug dose at 75 mg/m2: 1.8136 x 75 = 136.0 mg Cardiac index: 5.0 / 1.8136 = 2.76 L/min/m2
Result:BSA: 1.8136 m2 | Sample dose (75 mg/m2): 136.0 mg | Cardiac Index: 2.76
Example 2: Pediatric BSA Calculation
Problem:Calculate BSA for a child weighing 25 kg and 120 cm tall.
Solution:DuBois: BSA = 0.007184 x 25^0.425 x 120^0.725 = 0.007184 x 4.217 x 39.09 = 1.1841 m2 Haycock: BSA = 0.024265 x 25^0.5378 x 120^0.3964 = 0.024265 x 5.476 x 8.858 = 0.9271 m2 The Haycock formula is preferred for children and gives a lower estimate. Drug dose at 100 mg/m2 (Haycock): 0.9271 x 100 = 92.7 mg
Result:BSA (Haycock): 0.9271 m2 | BSA (DuBois): 1.1841 m2 | Dose (100 mg/m2): 92.7 mg
Frequently Asked Questions
What is Body Surface Area and why is it medically important?
Body Surface Area (BSA) is the total area of the external surface of the human body, measured in square meters. BSA is a critical measurement in clinical medicine because many physiological processes scale more closely with surface area than with body weight alone. It is most commonly used in oncology to calculate chemotherapy drug dosages, where even small dose variations can mean the difference between therapeutic efficacy and dangerous toxicity. BSA is also used to calculate the cardiac index (cardiac output divided by BSA), determine fluid resuscitation volumes for burn patients (using the rule of nines), adjust renal function markers like glomerular filtration rate, and set pediatric drug doses. The average adult BSA is approximately 1.7 m2 for women and 1.9 m2 for men.
How is BSA used in chemotherapy dosing?
Chemotherapy drugs are among the most toxic medications used in clinical practice, with narrow therapeutic windows between effective treatment and dangerous side effects. BSA-based dosing adjusts the drug amount to the patient's body size, theoretically accounting for differences in drug distribution, metabolism, and clearance. A typical chemotherapy dose might be prescribed as 75 mg/m2 of BSA, meaning a patient with BSA of 1.8 m2 would receive 135 mg. While BSA-based dosing has been standard practice for over 50 years, recent research suggests it does not perfectly predict drug pharmacokinetics, and some newer targeted therapies use flat (fixed) dosing instead. Nevertheless, BSA remains the standard for most cytotoxic chemotherapy agents.
How does BSA differ from BMI in assessing body size?
BSA and BMI both use height and weight but measure fundamentally different things. BMI (weight/height-squared) is a ratio that categorizes weight status (underweight, normal, overweight, obese) and is primarily used for epidemiological screening and general health assessment. BSA estimates the actual external surface area of the body in square meters and is used for clinical calculations like drug dosing and physiological indices. Two people with the same BMI can have different BSAs if their height and weight combinations differ. For example, a short heavy person and a tall lean person might share a BMI of 25 but have very different surface areas. BSA increases with both height and weight but is not a simple ratio; it follows a power-law relationship described by the various BSA formulas.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator ยท Editorial policy
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