Body Surface Area (BSA) Calculator
Estimate body surface area using the Mosteller, DuBois, and Haycock formulas.
What Is the Body Surface Area (BSA) Calculator?
Body Surface Area (BSA) Calculator Formula
Mosteller: BSA = √(Height(cm) × Weight(kg) ÷ 3600)
How Is the Body Surface Area (BSA) Calculator Calculated?
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).
Body Surface Area (BSA) Calculator Example
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 the Body Surface Area (BSA) Calculator
Step 1
Enter your weight and select kg or lbs.
Step 2
Enter your height in centimeters.
Step 3
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.
Common Body Surface Area (BSA) Calculator Scenarios
Scenario 1
Understanding how a doctor or pharmacist may have calculated a BSA-based medication dose.
Scenario 2
Nursing, pharmacy, or medical student coursework involving dosing calculations.
Scenario 3
General curiosity about total skin surface area relative to height and weight.
Understanding Your Result
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.
Frequently Asked Questions
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.
How is BSA different from BMI?
BSA estimates total skin surface area and is used mainly for drug dosing, while BMI estimates a weight-to-height ratio used for weight-category screening — they serve different clinical purposes and aren't interchangeable.
Why do doctors use BSA instead of weight alone for chemotherapy dosing?
BSA correlates more closely with blood volume, cardiac output, and metabolic rate than body weight alone, which gives safer and more consistent dosing across patients of different sizes.
What's the difference between the DuBois and Haycock formulas?
DuBois (1916) was one of the earliest BSA formulas, derived from a small direct-measurement study, while Haycock (1978) was developed specifically to be more accurate for infants and children.
Does my BSA change if I lose or gain weight?
Yes — since weight is one of the two inputs, a meaningful change in weight will shift your calculated BSA even if your height stays the same.
Is BSA used for anything besides drug dosing?
Yes, it's also used to calculate cardiac index (cardiac output relative to body size) and in some burn-severity assessments in clinical settings.
Important Information
This tool is for educational and informational purposes only and must never be used to calculate actual medication dosages.
Last updated: July 26, 2026