What is Body Surface Area?
Body Surface Area (BSA) is the measured or calculated total surface area of a human body. Unlike Body Mass Index (BMI), which is merely a ratio of weight to height used to estimate body fat, BSA provides an estimation of metabolic mass. Because it is much less affected by abnormal adipose (fat) tissue mass, it is widely considered a far superior metabolic indicator than body weight alone.
Clinical Applications of BSA
In modern medicine, BSA is a highly critical metric utilized primarily for safely calculating medication dosages. Calculating dosages based strictly on body weight can be extremely dangerous—especially for patients who are obese or emaciated.
- Chemotherapy: Almost all oncology treatments and chemotherapy agents are dosed per square meter of BSA to minimize severe toxic side effects.
- Glucocorticoids: Dosing for potent steroids is heavily reliant on BSA.
- Cardiac Index: Cardiologists use BSA to calculate a patient's Cardiac Index (cardiac output divided by BSA), providing a more accurate assessment of heart performance than cardiac output alone.
The Formulas Explained
Over the last century, numerous mathematical formulas have been developed to estimate BSA without having to physically measure a patient's skin. Our calculator outputs the results for the three most prominent medical formulas:
The Mosteller Formula (1987)
Currently the most widely used formula in practice due to its simplicity and high degree of accuracy for both adults and children. It is the default formula used by most modern EMR systems.
The DuBois & DuBois Formula (1916)
The original pioneer formula for calculating BSA. While it has been largely superseded by Mosteller in general practice, it is still the preferred formula in many older clinical oncology trials.
The Haycock Formula (1978)
Specifically developed to be accurate across a wider spectrum of body shapes, particularly for infants and small children where the DuBois formula historically underestimated BSA.