BSA Calculator
Calculate your Body Surface Area using the Du Bois and Mosteller formulas. BSA is used in medicine, fitness, and metabolic assessments.
What is Body Surface Area (BSA)?
Body Surface Area (BSA) is a measurement of the total surface area of the human body, expressed in square meters (m²). Unlike body weight alone, BSA accounts for both height and weight, providing a more accurate representation of metabolic mass.
BSA is a critical measurement in clinical medicine. It is used to calculate appropriate drug dosages, particularly for chemotherapy agents where precise dosing is essential. Many medications, especially those with a narrow therapeutic index, are dosed based on BSA rather than body weight to improve safety and efficacy.
Beyond drug dosing, BSA is used to assess burn severity (the “rule of nines” estimates burned BSA), calculate cardiac output indices, calibrate medical equipment such as ventilators, and evaluate renal function through glomerular filtration rate (GFR) normalization.
The Du Bois Formula
The Du Bois formula, published in 1916 by D. Du Bois and E.F. Du Bois, is the most widely used and validated BSA formula in clinical practice:
BSA (m²) = 0.007184 × Weight (kg)0.425 × Height (cm)0.725
This formula was derived from direct measurements of only nine subjects but has proven remarkably accurate across a wide range of body sizes. It remains the gold standard for BSA calculation in most clinical guidelines and drug dosing protocols.
The Mosteller Formula
The Mosteller formula, proposed by R.D. Mosteller in 1987, offers a simplified alternative to the Du Bois formula:
BSA (m²) = √((Height (cm) × Weight (kg)) / 3600)
This formula is easier to compute and is widely used in pediatric medicine and research settings. Studies have shown it produces results that are very close to the Du Bois formula, typically within 1-2%. Its simplicity makes it convenient for quick bedside calculations.
Typical BSA Values
Understanding typical BSA ranges can help you contextualize your results:
- Adult men: Average BSA is approximately 1.9 m², typically ranging from 1.7 m² to 2.2 m².
- Adult women: Average BSA is approximately 1.6 m², typically ranging from 1.4 m² to 1.9 m².
- Newborns: Approximately 0.25 m².
- Children (10 years): Approximately 1.1 m².
These values can vary significantly based on individual body composition. Athletes and taller individuals tend to have higher BSA values, while smaller-framed or shorter individuals will have lower values.
Frequently Asked Questions
What is BSA used for?
Body Surface Area is primarily used in medicine for calculating drug dosages (especially chemotherapy), determining burn severity, estimating cardiac output, and adjusting medical device settings. It provides a more accurate measure of metabolic mass than body weight alone.
How is BSA calculated?
BSA is most commonly calculated using the Du Bois formula: BSA = 0.007184 × Weight(kg)0.425 × Height(cm)0.725. The Mosteller formula provides a simpler alternative: BSA = √((Height × Weight) / 3600). Both give results in square meters.
What is a normal BSA?
The average BSA for adult men is approximately 1.9 m² and for adult women is approximately 1.6 m². BSA values typically range from about 1.2 m² to 2.4 m² for adults. Newborns have a BSA of approximately 0.25 m².
Du Bois vs Mosteller: Which is better?
Both formulas are clinically validated and produce very similar results, usually within 1-2% of each other. The Du Bois formula is the gold standard used in most drug dosing guidelines. The Mosteller formula is simpler and commonly used in pediatrics. For general purposes, either formula is appropriate.