You’ve probably heard of BMI (Body Mass Index) in reference to overall health, weight loss or exercise, but what about BSA (Body Surface Area)? How is this different from BMI and how is it calculated? Moreover, why should you care?   

While Body Mass Index (BMI) is a measure of a person’s body fat mass, Body Surface Area measures the total surface area of a person’s body and is frequently used in order to calculate drug dosage and the amount of fluids to be administered by IV.

Various formulas have been used over the last century to calculate BSA. They all give slightly different results, which has created issues of standardization. For the sake of example, the Mosteller formula is commonly referred to and often used in clinical trials. It calculates BSA by taking the square root of height (cm) multiplied by weight (kg) divided by 3600.

Many online calculators offer the conversion from centimeters to inches and from kilograms to pounds, which makes calculating one’s own BSA fairly easy. Take, for instance, a woman who is five feet, 5 inches tall (65 inches) and who weighs 150 pounds. This calculator allows you to select inches and pounds and the type of formula you want to use. You’ll see that the woman in this example has a BSA of 1.75 m2  (meters squared) using the DuBoise formula. 

Body surface area measurement, in medical terms, has many significant implications. For example, it is used during the clinical assessment and diagnosis of Vitiligo, a chronic disorder that causes patches of skin to lose pigment. According to the journal Pediatrics, topical therapies for Vitiligo can be used solely in limited surface involvement (<20% of body surface area) or in combination with other treatments, mainly phototherapy, in wider involvement (>20% of body surface area).

It is also routinely calculated in the cardiovascular field, and research has shown that body surface area is a strong predictor of mortality in chronic heart failure patients. 

Also, BSA calculation is used in chemotherapy dosing, with the idea that each patient receives an individualized dose of chemo specific to their height and weight. 

While no means a full list of the many applications of body surface area measurement, the conditions described illustrate the vital importance of this metric in health and wellness assessments.

This blog is intended to be informational in nature. The information and other content provided in this blog, or in any linked materials, are not intended and should not be construed as medical advice, nor is the information a substitute for professional medical expertise or treatment.

If you have any questions or concerns, please talk to your doctor. Never disregard professional medical advice or delay in seeking it because of something you have read on this blog or in any linked materials. If you think you may have a medical emergency, call your doctor or emergency services immediately.