What is body surface area (BSA)?

BSA is the estimated total surface area of the body in square meters. It correlates better with metabolic rate and blood flow than weight alone, which is why medicine uses it for drug dosing and cardiac measurements.

How is BSA calculated?

The widely used Mosteller formula is BSA = √(height(cm) × weight(kg) ÷ 3600). Other established formulas include Du Bois and Haycock, which give slightly different results; clinicians generally pick one and use it consistently.

Why is BSA used for medication dosing?

Drugs with narrow safety margins — chemotherapy in particular — are dosed per square meter of BSA because clearance and metabolism track body surface better than raw weight. This helps standardize exposure across patients of very different sizes.

What is a typical adult BSA?

The often-cited average is about 1.7 m² — roughly 1.9 m² for adult men and 1.6 m² for adult women. Children's values are much smaller, which is one reason pediatric doses are calculated rather than scaled down informally.

Is BSA the same as BMI?

No. BMI (weight ÷ height²) screens for weight category, while BSA estimates physical surface area for clinical calculations. Two people can share a BMI but have different BSAs, and the two numbers are used for entirely different purposes.

Body Surface Area Calculator

Calculate body surface area for medical dosing and health assessments. Free, fast, accurate — no signup, mobile-friendly

Patient Information

Age (years)

Gender

Height Unit

Height (cm)

Weight Unit

Weight (kg)

BSA Formula

👤 Sample Patients

🏥 Formula Information

DuBois: Most widely used, established in 1916

Mosteller: Simplest calculation, good accuracy

Haycock: Good for pediatric patients

Boyd: Most complex, highest accuracy claimed

BSA Results

Body Surface Area

1.81 m²

dubois formula

Normal Range

1.5 - 2.0 m²

Adult reference

Formula Comparison

DuBois & DuBois:1.81 m²

Mosteller:1.818 m²

Haycock:1.826 m²

Gehan & George:1.831 m²

Boyd:0.029 m²

Medical Applications

Drug Dosing: For chemotherapy: Consider 181 mg/m² dosing

Cardiac Output: Normal CO ≈ 4.53 L/min

Burn Assessment: For burn area: Use BSA to calculate percentage of total body surface area affected

📋 Calculation Details

1DuBois: 0.007184 × 70.0^0.425 × 170.0^0.725 = 1.810 m²

2Mosteller: √((170.0 × 70.0) / 3600) = 1.818 m²

3Haycock: 0.024265 × 70.0^0.5378 × 170.0^0.3964 = 1.826 m²

4Gehan & George: 0.0235 × 70.0^0.51456 × 170.0^0.42246 = 1.831 m²

5Boyd: 0.0003207 × 170.0^0.3 × 70.0^(0.7285 - 0.0188×log10(70.0)) = 0.029 m²

How it works

Body surface area (BSA) estimates the total external area of the body, used in medicine to size drug doses and assess burns. The Mosteller formula is the most common: the square root of height times weight, divided by 3600.

Mosteller BSA

BSA (m²) = √( height(cm) × weight(kg) ÷ 3600 )

height: in centimetres
weight: in kilograms

Worked example

Height = 175 cm
Weight = 70 kg

175 × 70 ÷ 3600 = 3.403
BSA = √3.403

BSA ≈ 1.85 m².

Good to know

BSA is preferred over weight for dosing many chemotherapy and other drugs because it tracks metabolic rate better.
Several formulas (Du Bois, Haycock) give slightly different values — clinicians pick one and stay consistent.
Average adult BSA is roughly 1.7 m².