Body Surface Area Calculator
Calculate your body surface area using the Mosteller formula — essential for clinical drug dosing.
About Body Surface Area
Body Surface Area (BSA) is used in medicine to calculate drug doses (especially chemotherapy), burn area assessment, and pediatric drug dosing. The Mosteller formula — √(height×weight/3600) — is the most widely adopted due to its simplicity and accuracy.
Accuracy The Mosteller formula estimates BSA within ±5% of direct measurements for most adults. Results may be less precise for individuals with very high or very low BMI. For clinical dosing, always verify with a healthcare professional.
BSA Formulas Compared
| Formula | Equation |
|---|---|
| Mosteller (recommended) | √(H × W / 3600) m² |
| DuBois & DuBois | 0.007184 × H^0.725 × W^0.425 m² |
Average adult BSA ≈ 1.7–1.9 m²
What to do with your result
- Share your BSA value with your doctor or oncologist before starting any drug therapy that uses BSA-based dosing.
- If your BSA is below 1.7 m², alert your care team — reduced surface area can affect standard drug dose calculations.
- Track changes over time: recalculate BSA if you gain or lose more than 5 kg, especially during chemotherapy.
- Use the Mosteller result as the primary reference; the DuBois value is useful as a cross-check for clinical decisions.
Frequently Asked Questions
What is body surface area (BSA) used for?
BSA is used in medicine to calculate doses of chemotherapy drugs, burn treatment area, and pediatric medications. It is a more accurate scaling factor than body weight alone because it correlates better with metabolic rate and organ function.
Which BSA formula is most accurate?
The Mosteller formula (√(height × weight / 3600)) is the most widely used in clinical practice due to its simplicity and good accuracy. The DuBois & DuBois formula is older and slightly less accurate for extremes of body size, but both agree within about 5% for most adults.
What is the average BSA for an adult?
The average adult BSA is approximately 1.7–1.9 m². Men average around 1.9 m² and women around 1.7 m². Children have smaller BSA values that increase progressively with age.
Does BSA change with weight loss or gain?
Yes. BSA increases with higher weight and height, and decreases with weight loss. Drug dosing based on BSA is recalculated if a patient's weight changes significantly (typically more than 10%) during treatment.
Is BSA the same as body surface area used in burn assessments?
Yes, but burn assessments also use the Rule of Nines — a separate method that estimates what percentage of the total BSA is burned. The Mosteller or DuBois BSA value is used to express the total skin area, while the Rule of Nines expresses burn coverage as a percentage.
This calculator is for educational purposes only. Consult a qualified healthcare professional for medical advice.