Body Surface Area Calculator

Complete BSA Calculator Guide & Information

1. What is Body Surface Area (BSA)?

Body Surface Area (BSA) is the total surface area of the human body measured in square meters or square feet. It is a critical measurement in medicine and physiology because it correlates more closely with metabolic rate, fluid requirements and drug metabolism than body weight alone.

BSA is widely used to calculate medication dosages (especially chemotherapy agents), assess cardiac index, estimate glomerular filtration rate, determine fluid replacement for burn patients, and evaluate metabolic demand. Direct measurement of BSA is impractical in clinical settings, so various empirical formulas have been developed to estimate it from height and weight.

2. BSA Calculation Formulas

Formula	Equation	Notes
Du Bois & Du Bois	BSA = 0.007184 × W0.425 × H0.725	Most widely used classic formula (1916). Standard in most clinical settings.
Mosteller	BSA = √( W × H / 3600 )	Simplest formula. Widely accepted and easy to calculate.
Haycock et al.	BSA = 0.024265 × W0.5378 × H0.3964	Commonly used in pediatric nephrology.
Gehan & George	BSA = 0.0235 × W0.51456 × H0.42246	Improved version of Du Bois across wider weight range.
Boyd	BSA = 0.03330 × W(0.6157 - 0.0188 × log₁₀W) × H0.3	More complex formula, accurate at extremes of body size.
Fujimoto	BSA = 0.008883 × W0.444 × H0.663	Developed for Japanese populations.
Takahira	BSA = 0.007241 × W0.425 × H0.725	Asian population-specific formula.
Schlich	Male: 0.0009754 × W0.46 × H1.08 Female: 0.0009754 × W0.46 × H1.06	Gender-specific 3D scan-based formula (2010).

W = body weight in kilograms, H = body height in centimeters. All results in m².

3. Unit Conversions

Unit	Conversion Factor
1 square meter (m²)	= 10.7639 square feet (ft²)
1 square meter (m²)	= 1550 square inches (in²)
1 kilogram (kg)	= 2.20462 pounds (lbs)
1 centimeter (cm)	= 0.393701 inches (in)
1 foot (ft)	= 30.48 centimeters (cm)

4. Common Clinical Uses of BSA

• Chemotherapy dosing: Most cancer drugs are dosed by BSA to balance efficacy and toxicity.
• Cardiac index: Cardiac output divided by BSA gives normalized cardiac function measure.
• Renal function: GFR is standardized to 1.73 m² BSA for comparison across individuals.
• Burn care: Fluid resuscitation formulas (Parkland, Brooke) use BSA and percentage of burns.
• Metabolic rate: Basal metabolic rate correlates closely with body surface area.
• Pediatric dosing: Medication dosages for children are often adjusted by BSA.

5. BSA vs BMI

BMI (Body Mass Index) describes weight relative to height and is used to classify weight categories. BSA describes total surface area and is used for physiological and pharmacological calculations. While both use height and weight, they serve different purposes. BMI is simpler and used for population-level health screening, while BSA is more relevant for individual clinical dosing and assessment.

Average BSA for adult men is approximately 1.9 m² and for adult women approximately 1.6 m², but values vary significantly with body size and composition.

6. Input & Control Definitions

• Gender: Select male or female. Used in gender-specific formulas like Schlich.
• Body Weight: Current body weight. Select units: pounds or kilograms.
• Body Height (feet + inches): Imperial height input. Automatically converts to centimeters.
• Body Height (cm): Metric height input. Automatically converts to feet and inches.
• Calculate Button: Computes all 8 BSA formulas in three units plus BMI.
• Clear Button: Resets all inputs to default values.

7. Limitations & Considerations

• All formulas are estimates. Actual BSA varies with body composition, muscle mass and body shape.
• Formulas were developed on specific populations and may be less accurate at extremes of size, age or ethnicity.
• BSA should not be used as the sole determinant of drug dosing. Clinical judgment and other factors must be considered.
• For obese patients, ideal body weight or adjusted body weight may produce more accurate dosing estimates.
• 3D body scanning provides the most accurate BSA measurement but is rarely available in routine practice.

8. Medical Disclaimer

This calculator is for educational and informational purposes only. It is NOT a substitute for professional medical advice, diagnosis or treatment. BSA calculations are estimates and should always be interpreted and applied by qualified healthcare professionals.

Do not make medical decisions or adjust medication dosages based on these calculations. Always consult a physician, pharmacist or other qualified healthcare provider for clinical decisions.

9. References

1. Du Bois D, Du Bois EF. "A formula to estimate the approximate surface area if height and weight be known." Archives of Internal Medicine. 1916.
2. Mosteller RD. "Simplified calculation of body-surface area." New England Journal of Medicine. 1987.
3. Haycock GB, Schwartz GJ, Wisotsky DH. "Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults." Journal of Pediatrics. 1978.
4. Gehan EA, George SL. "Estimation of human body surface area from height and weight." Cancer Chemotherapy Reports. 1970.
5. Boyd E. "The growth of the surface area of the human body." University of Minnesota Press. 1935.
6. Schlich E, et al. "3D body scanning: new equations for body surface area in adults." European Journal of Clinical Nutrition. 2010.