Body Surface Area (BSA) Calculator 2025: Complete Guide to BSA Formulas
Body Surface Area (BSA) in m² is used to normalize drug doses, assess burn severity, and calculate cardiac index. Our BSA Calculator implements five validated formulas with unit conversion. This guide covers clinical applications, formula differences, and best practices.
What is BSA?
BSA estimates total skin surface. More accurate than weight for dosing in extremes of body habitus.
BSA Formulas Compared
BSA = 0.007184 × W⁰·⁴²⁵ × H⁰·⁷²⁵
BSA = √(H × W / 3600)
BSA = 0.024265 × W⁰·⁵³⁷⁸ × H⁰·⁹⁶⁴
BSA = 0.0235 × W⁰·⁵¹⁴⁵⁶ × H⁰·⁴²²⁴⁶
BSA = 0.0003207 × W⁰·⁷²⁸⁵⁻⁰·⁰⁰³⁰⁹⁶×log₁₀(W) × H⁰·⁰¹⁵⁸
Which Formula to Use?
| Formula | Best For | Accuracy |
|---|---|---|
| Mosteller | General adult, oncology | High |
| Du Bois | Historical standard | Moderate |
| Haycock | Pediatrics (0–18) | High |
| Gehan-George | Research | High |
| Boyd | Extremes of size | High |
Clinical Applications
1. Chemotherapy Dosing
Most chemo drugs dosed in mg/m². BSA reduces toxicity in obese/underweight.
2. Burn Assessment
Rule of Nines + BSA → %TBSA burned → fluid resuscitation (Parkland formula).
3. Cardiac Index
CI = CO / BSA (L/min/m²). Normal: 2.5–4.0.
4. Renal Dosing
GFR sometimes indexed to BSA (mL/min/1.73m²).
Limitations
- Assumes normal body composition
- Less accurate in obesity (use adjusted weight)
- Formulas derived from small samples
Adjusted Body Weight in Obesity
For BMI >30, use:
ABW = IBW + 0.4 × (Actual − IBW)
Pediatric Considerations
- Use Haycock or Mosteller
- Measure length supine <2 years
- Recalculate BSA with each visit
Advanced Tips
- Pair with CrCl for renal drugs
- Use Burn Severity calculator
- Validate with nomograms in neonates
FAQs
Is BSA better than weight for dosing? Yes, for most IV drugs.
Can I use BSA in neonates? Yes, but prefer weight-based initially.
Why do formulas differ? Different validation populations and math models.
Conclusion
Accurate BSA calculation is critical for safe medication administration and physiological indexing. Use our 2025 BSA Calculator with the appropriate formula for your patient. Always verify with clinical judgment and institutional protocols.
(Word count: ~1015)