Body Surface Area (BSA) Calculation Formula
The Mosteller formula is the recommended method for calculating BSA in clinical practice due to its simplicity and ease of use: BSA (m²) = √[(Height(cm) × Weight(kg))/3600] 1
Primary BSA Formulas for Clinical Use
Mosteller Formula (Preferred for General Clinical Use)
- BSA (m²) = √[(Height(cm) × Weight(kg))/3600] is recommended by the American Society of Clinical Oncology for drug dosing calculations due to its simplicity and clinical applicability 1
- This formula can be easily remembered and calculated on a pocket calculator, making it practical for bedside use 2
- Research demonstrates excellent correlation (r² = 0.991) with other established formulas across a wide range of patient sizes 3
Gehan and George Formula (Preferred for Pediatric Patients)
- BSA (m²) = 0.0235 × (height [cm])^0.42246 × (weight [kg])^0.51456 is specifically recommended for pediatric patients 4, 5
- The American Academy of Pediatrics and British National Formulary for Children recommend this equation because it was derived from the greatest number of study subjects 5, 1
- This formula is particularly important for pediatric peritoneal dialysis patients when estimating total body water 4, 5
Clinical Applications Requiring BSA
Chemotherapy Dosing
- BSA is essential for calculating doses of chemotherapeutic agents, which are frequently dosed based on m² to account for variations in drug metabolism and clearance 1
- For medications with narrow therapeutic indices, precise BSA calculation is critical to avoid toxicity while maintaining efficacy 5, 1
Pediatric Applications
- BSA-based dosing is particularly important in pediatric patients due to developmental differences in drug metabolism 1
- BSA is used to normalize cardiac parameters, evaluate coronary artery dimensions in Kawasaki disease, and calculate peritoneal dialysis prescriptions 5
Special Population Considerations
Obese Patients
- The traditional DuBois formula underestimates BSA in obese patients by 3% (male) to 5% (female) 2
- Standard BSA formulas may be less accurate in patients with abnormal body composition including obesity, edema, or cachexia 1
Malnourished or Amputee Patients
- BSA calculations may need adjustment using established tables for weight and BSA corrections 5
- In malnourished patients, calculations may need to account for desired rather than actual weight 5
Alternative Simplified Formula for Pediatrics
- A weight-based formula BSA = (4W + 7)/(90 + W) where W is weight in kg, provides excellent correlation with Mosteller formula and eliminates the need for height measurement 3
- This simplified approach is particularly useful in emergency or resource-limited settings where height measurement may be difficult 3
Common Pitfalls to Avoid
- Never use serum creatinine alone to assess kidney function when calculating medication doses that require BSA normalization, as creatinine significantly overestimates clearance 6
- For medications requiring renal clearance, creatinine clearance should be considered alongside BSA for appropriate dosing 1
- Ensure optimal hydration status before initiating potentially toxic drug therapy that requires BSA-based dosing 6