How BSA is calculated
Body surface area is estimated from height and weight. The Mosteller formula is the simplest and most widely used:
BSA (m²) = √( Height(cm) × Weight(kg) ÷ 3600 )
For someone 180 cm and 75 kg: √(180 × 75 ÷ 3600) = √3.75 ≈ 1.94 m². Imperial inputs are converted first — inches × 2.54 for centimeters and pounds × 0.4536 for kilograms.
Other formulas
- Du Bois: 0.007184 × height0.725 × weight0.425 — the historical standard.
- Haycock: 0.024265 × height0.3964 × weight0.5378 — works well for children and adults.
For most adults the three formulas land within a few percent of each other, so the average gives a robust single figure.
Why BSA matters
The average adult BSA is roughly 1.7 m². Clinicians use BSA to dose certain medications — chemotherapy especially — and to index measurements like cardiac output, because surface area tracks metabolic size better than weight alone.
Frequently asked questions
What is body surface area (BSA)?
Body surface area is the total surface area of the human body, measured in square meters (m²). It is widely used in medicine — especially to calculate drug doses and to index measures like cardiac output — because it tracks metabolic mass better than body weight alone.
How is BSA calculated?
BSA is estimated from height and weight using established formulas. The Mosteller formula is the most common: BSA (m²) = √(height in cm × weight in kg ÷ 3600). The Du Bois and Haycock formulas use power equations and give very similar results.
What is the average body surface area?
The average adult BSA is often cited as about 1.7 m² — roughly 1.6 m² for women and 1.9 m² for men. Children are much smaller; a newborn is around 0.25 m². Your exact value depends on your height and weight.
Which BSA formula should I use?
The Mosteller formula is the most widely used because it is simple and accurate, and it is the default here. Du Bois is the historical standard still referenced in many texts, and Haycock works well across all ages including children. For most adults the three agree within a few percent.
Why is BSA used for medication dosing?
Many drugs — chemotherapy in particular — are dosed per square meter of body surface area because BSA correlates with metabolic rate, blood volume, and organ size more reliably than weight. This helps deliver an effective dose while limiting toxicity.
Disclaimer: This calculator provides BSA estimates for educational purposes only. It is not medical advice and must not be used to determine medication doses — that is a task for a qualified healthcare professional.