Du Bois Body Surface Area Formula
Calculate body surface area using the Du Bois formula: BSA = 0.007184 x W^0.425 x H^0.725.
Used for drug dosing and burn assessment.
The Formula
The Du Bois body surface area formula was published in 1916 by Delafield Du Bois and Eugene Du Bois, two American physicians who studied the relationship between body dimensions and skin surface area. Despite being over a century old, it remains one of the most widely used BSA formulas in clinical medicine today.
Body surface area is a measurement of the total area of the outer surface of the human body. It is considered a more accurate indicator of metabolic mass than body weight alone because many physiological processes, including heat loss, drug metabolism, and organ function, correlate more closely with surface area than with weight. An average adult has a BSA of approximately 1.7 m² (about 18.3 ft²), though this varies significantly depending on body size.
In medicine, BSA is essential for calculating correct drug dosages, particularly in chemotherapy where many anti-cancer drugs are dosed in milligrams per square meter (mg/m²). This approach helps standardize dosing across patients of different sizes and reduces the risk of overdosing smaller patients or underdosing larger ones. BSA is also critical in burn treatment, where the percentage of body surface affected by burns determines fluid resuscitation requirements and treatment severity classification.
Other applications include calculating cardiac index (cardiac output divided by BSA), determining renal function, and setting ventilator parameters. The Du Bois formula requires weight in kilograms and height in centimeters. For imperial measurements, convert pounds to kilograms by dividing by 2.205 and inches to centimeters by multiplying by 2.54.
Several alternative BSA formulas exist, including the Mosteller formula (BSA = √(W × H / 3600)) and the Haycock formula, but the Du Bois formula remains the clinical standard in most institutions worldwide.
Variables
| Symbol | Meaning |
|---|---|
| BSA | Body Surface Area (square meters, m²) |
| W | Body weight (kilograms, kg) |
| H | Height (centimeters, cm) |
Example 1
Calculate the BSA for a person weighing 70 kg and 175 cm tall.
BSA = 0.007184 × 700.425 × 1750.725
700.425 = 6.396
1750.725 = 46.18
BSA = 0.007184 × 6.396 × 46.18
BSA ≈ 1.85 m²
Example 2
A patient weighing 154 lbs and 5'6" tall needs a chemotherapy dose of 75 mg/m². What is their BSA and required dose?
Convert: 154 lbs ÷ 2.205 = 69.84 kg
Convert: 5'6" = 66 inches × 2.54 = 167.6 cm
BSA = 0.007184 × 69.840.425 × 167.60.725
BSA ≈ 1.78 m²
Dose = 75 mg/m² × 1.78 m²
BSA ≈ 1.78 m², Drug dose ≈ 133.5 mg
When to Use It
Use the Du Bois BSA formula when you need to:
- Calculate chemotherapy or other drug dosages that are prescribed per m²
- Assess burn severity and determine fluid resuscitation volumes
- Calculate cardiac index (cardiac output / BSA) for hemodynamic monitoring
- Determine glomerular filtration rate adjustments for kidney function
- Set mechanical ventilation parameters based on patient size
Always use actual measured weight and height for clinical calculations. The formula is most accurate for adults of normal body proportions and may be less reliable for very obese patients or young children.