Body Surface Area Calculator
Calculate Body Surface Area (BSA) using multiple clinically validated formulas. BSA is essential for accurate drug dosing, especially chemotherapy.
About This Calculator
How to Use
- Select your preferred unit system (Metric or Imperial)
- Enter your height
- Enter your weight
- Click Calculate to see BSA from all formulas
- Use Mosteller result for most clinical applications
📚 Understanding Body Surface Area
Body Surface Area (BSA) is a measurement of the total surface area of the human body, expressed in square meters (m²). Unlike weight alone, BSA accounts for both height and weight, providing a more accurate representation of body size for medical calculations.
BSA is particularly important because many physiological processes (metabolism, heat loss, drug clearance) correlate better with surface area than with weight alone. This is why BSA-based dosing is preferred for medications with narrow therapeutic windows.
Average values: Adult male ~1.9 m², Adult female ~1.6 m², Newborn ~0.25 m²
🧮 BSA Formulas
BSA = sqrt(height x weight / 3600)
BSA = 0.007184 x height^0.725 x weight^0.425
BSA = 0.024265 x height^0.3964 x weight^0.5378
BSA = 0.0235 x height^0.42246 x weight^0.51456
BSA = 0.0003207 x height^0.3 x weight^(0.7285 - 0.0188 x log10(weight))
Note: All formulas use height in cm and weight in kg. Results typically agree within 5%.
💡 Clinical Applications
- Chemotherapy Dosing: Most cytotoxic drugs are dosed per m² BSA
- Cardiac Index: Cardiac output / BSA = Cardiac Index
- Burn Assessment: Calculate percentage of body surface burned
- Renal Function: Standardize GFR to 1.73 m² BSA
- Pediatric Dosing: More accurate than weight-based dosing for many drugs
- Radiation Therapy: Calculate treatment doses
- Fluid Resuscitation: Calculate maintenance fluids
❓ Frequently Asked Questions
Which BSA formula should I use?
The Mosteller formula is most commonly used in clinical practice due to its simplicity and accuracy. For pediatric patients, the Haycock formula may be preferred. Follow your institution's protocol if specified.
Why do formulas give slightly different results?
Each formula was developed using different study populations and methods. Differences are usually within 5% and clinically insignificant. Most modern protocols use Mosteller or specify which formula to use.
What is a normal BSA?
Average adult BSA is approximately 1.7-2.0 m². Men typically have larger BSA (~1.9 m²) than women (~1.6 m²). BSA varies widely based on body size.
Why not just use body weight for drug dosing?
BSA better correlates with metabolic rate and drug clearance than weight alone. This is especially important for drugs with narrow therapeutic windows (like chemotherapy) where overdosing can be toxic and underdosing ineffective.