Body Surface Area (BSA) Calculator
Estimate body surface area using the Mosteller, DuBois, and Haycock formulas.
What is it?
Body Surface Area (BSA) is an estimate of the total surface area of the human body, used mainly in medicine to calculate drug dosages, chemotherapy doses, and other clinical measurements more precisely than weight alone.
Formula
Mosteller: BSA = √(Height(cm) × Weight(kg) ÷ 3600)
Formula Explanation
The Mosteller formula is a simplified square-root formula widely used in clinical settings for its ease of calculation. The DuBois and Haycock formulas use power functions derived from direct body-surface measurement studies and are considered more precise for certain populations, such as infants (Haycock).
Example Calculation
A person weighing 70 kg at 170 cm tall has a Mosteller BSA of √(170 × 70 ÷ 3600) = 1.82 m², close to the commonly cited average adult BSA of 1.7-2.0 m².
How to Use
- Enter your weight and select kg or lbs.
- Enter your height in centimeters.
- Compare your BSA across the Mosteller, DuBois, and Haycock formulas.
Benefits
- Shows three clinically referenced formulas at once instead of just one.
- Useful for understanding how chemotherapy and other BSA-based drug doses are calculated.
- Simple, fast calculation using only height and weight.
Use Cases
- Understanding how a doctor or pharmacist may have calculated a BSA-based medication dose.
- Nursing, pharmacy, or medical student coursework involving dosing calculations.
- General curiosity about total skin surface area relative to height and weight.
What Your Result Means
The result is expressed in square meters (m²) and represents an estimate of your total body surface area. Clinicians use BSA rather than weight alone for drug dosing because it correlates more closely with metabolic rate and organ function across different body sizes.
Tips
- The Mosteller formula is the most widely used in hospitals today due to its simplicity and accuracy.
- The Haycock formula is generally preferred for infants and young children.
- Always rely on a clinician's calculation for actual medication dosing — this tool is for reference only.
Common Mistakes
- Using this tool to self-calculate medication doses — always defer to a licensed healthcare provider.
- Entering height in meters instead of centimeters, which will produce a drastically wrong result.
- Assuming all three formulas should match exactly — small differences between formulas are normal and expected.
FAQs
What is BSA used for?
BSA is primarily used in medicine to calculate drug dosages — especially chemotherapy — and to assess cardiac index and other metabolic measurements more accurately than body weight alone.
Which BSA formula is most accurate?
The Mosteller formula is most commonly used in clinical practice for its simplicity, while Haycock is often preferred for infants and DuBois remains a historical reference standard.
What is a normal BSA for an adult?
Average adult BSA is roughly 1.7 m² for women and 1.9 m² for men, though it varies with height and weight.
Can I use this to calculate my own medication dose?
No — this tool is for educational reference only. Medication dosing must always be calculated and verified by a licensed healthcare provider.
This tool is for educational and informational purposes only and must never be used to calculate actual medication dosages.
Last updated: July 26, 2026