Body Surface Area Converter
Our free human metrics converter handles body surface area conversions. See tables, ratios, and examples for quick reference.
Reviewed by Manoj Kumar, Mathematics Educator
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\n70^0.425 = 6.396\n170^0.725 = 49.95\nBSA = 0.007184 x 6.396 x 49.95 = 1.8136 m2\nMosteller check: sqrt((70 x 170) / 3600) = sqrt(3.306) = 1.8182 m2\nDrug dose at 75 mg/m2: 1.8136 x 75 = 136.0 mg\nCardiac 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\n= 0.007184 x 4.217 x 39.09 = 1.1841 m2\nHaycock: BSA = 0.024265 x 25^0.5378 x 120^0.3964\n= 0.024265 x 5.476 x 8.858 = 0.9271 m2\nThe Haycock formula is preferred for children and gives a lower estimate.\nDrug 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 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 by Manoj Kumar, Mathematics Educator · Editorial policy