What is Body Surface Area (BSA)?
Body Surface Area (BSA) is a measurement of the total area of the human body's skin, expressed in square meters (m2). It is a fundamental clinical parameter used in medicine for:
- Drug dosing, especially chemotherapy
- Burn assessment (rule of nines)
- Cardiac index calculation
- Glomerular filtration rate (GFR) determination
- Dialysis parameter adjustment
Calculation Formulas
Du Bois Formula (1916)
BSA = 0.007184 x weight^0.425 x height^0.725
The most widely used formula in clinical practice worldwide. It was developed by the Du Bois brothers by directly measuring the body surface area of patients.
Mosteller Formula (1987)
BSA = sqrt(height x weight / 3600)
A simplified formula that is easy to calculate even without a calculator. It provides results very close to Du Bois and is widely accepted.
Haycock Formula (1978)
BSA = 0.024265 x weight^0.5378 x height^0.3964
Developed specifically with pediatric populations, it is the preferred formula for calculating BSA in children and adolescents.
Reference Values
| Group | Average BSA (m2) | |-------|-------------------| | Newborn | 0.25 | | Child (2 years) | 0.5 | | Child (10 years) | 1.14 | | Average adult female | 1.6 | | Average adult male | 1.9 |
The average BSA value for an adult is approximately 1.7 m2. This value is frequently used as a reference for adjusting drug doses when individual measurements are not available.
Clinical Uses of BSA
Chemotherapy Dosing
Most chemotherapy agents are dosed in mg/m2 of body surface area. This allows for more precise dosing than relying on weight alone, as BSA correlates better with blood volume and metabolic function.
Cardiac Index
The cardiac index is calculated by dividing cardiac output by BSA:
CI = Cardiac Output (L/min) / BSA (m2)
The normal value is 2.5 to 4.0 L/min/m2.
Burn Assessment
BSA is used alongside the rule of nines to estimate the percentage of body surface area affected by burns, which is critical for determining treatment and fluid resuscitation.
BSA calculations for drug dosing must be performed and verified by healthcare professionals. This calculator is an educational and informational tool.
Which Formula Should I Use?
- Du Bois: Standard for most clinical applications in adults
- Mosteller: When a quick and simple calculation is needed
- Haycock: Preferred for pediatric patients
All three formulas produce very similar results for adults with average weight and height. Differences become more pronounced at extreme values of weight or height.
Body Surface Area (BSA) is the measurement of the total skin area of the body in square meters. In medicine, it is used to dose medications (especially chemotherapy), calculate cardiac index, assess burns, and adjust dialysis parameters.
Du Bois (1916) is the most commonly used clinical standard. Mosteller (1987) is a simplified version using square root. Haycock (1978) was developed for pediatric patients. All three give similar results in average adults.
The average adult BSA is approximately 1.7 m2. Males typically have a BSA close to 1.9 m2 and females around 1.6 m2. Values vary depending on weight and height.
BSA correlates better with blood volume, metabolic rate, and organ function than body weight alone. This allows for more precise and safer dosing, especially for drugs with a narrow therapeutic margin such as chemotherapy.
Yes. The Haycock formula is the most recommended for children. Pediatric dosing based on BSA is common for many medications. A newborn's BSA is approximately 0.25 m2 and increases with growth.
BSA formulas are estimates based on mathematical models. All formulas have an error margin of approximately 5-10%. For most clinical applications, this accuracy is sufficient. Direct measurement is more precise but impractical.
In burn evaluation, the patient's total BSA is used as a reference. The rule of nines divides the body into sections of 9% to quickly estimate the affected percentage. This is critical for calculating intravenous fluid resuscitation.