BSA Calculator
Calculate body surface area (BSA) using DuBois, Mosteller, and other formulas. Essential for chemotherapy dosing and cardiac index calculations.
BSA (Mosteller)
1.818 m²
Average
Typical adult range
All Formulas Comparison
DuBois (1916)
1.810 m²
Mosteller (1987)
1.818 m²
Haycock (1978)
1.826 m²
Gehan-George (1970)
1.831 m²
Boyd (1935)
0.029 m²
Fujimoto (1968)
1.764 m²
Average: 1.513 m²
Weight
70.0 kg
Height
170.0 cm
Example Drug Doses (Reference Only)
- • Doxorubicin (60 mg/m²): ~109 mg (60 mg/m²)
- • Paclitaxel (175 mg/m²): ~318 mg (175 mg/m²)
- • Carboplatin (AUC 5): ~9 mg (AUC 5)
These are examples only. Actual dosing requires clinical judgment.
Clinical Applications
- • Chemotherapy drug dosing
- • Cardiac index calculation (CI = CO/BSA)
- • Renal function normalization
- • Burn area assessment
- • Pediatric drug dosing
Disclaimer: This calculator is for educational purposes only. Drug dosing decisions should be made by qualified healthcare providers using appropriate clinical guidelines.
Related Calculators
About This Calculator
Body Surface Area (BSA) is a measurement used in medicine to more accurately determine drug dosages and assess physiological parameters. Unlike body weight alone, BSA accounts for both height and weight, providing a better approximation of metabolic mass. This calculator computes BSA using multiple validated formulas.
What is Body Surface Area? BSA is the measured or calculated surface area of a human body, typically expressed in square meters (m²). The average adult has a BSA of 1.7-2.0 m². BSA correlates better with metabolic rate, organ size, and physiological functions than body weight alone.
Why is BSA Important?
- Chemotherapy dosing: Most cancer drugs are dosed per m²
- Cardiac output normalization: Cardiac index = CO/BSA
- Renal function: eGFR is reported per 1.73 m²
- Burn assessment: Determining % body surface burned
- Pediatric dosing: More accurate than weight alone
Common Formulas:
- Mosteller (1987): Simple, widely used
- DuBois (1916): Historical standard
- Haycock (1978): Validated for children
For related health calculations, see our BMI Calculator and eGFR Calculator.
How to Use the BSA Calculator
- 1Enter your weight in kilograms or pounds.
- 2Enter your height in centimeters, inches, or feet/inches.
- 3Select the appropriate units for each measurement.
- 4View the calculated BSA using multiple formulas.
- 5The Mosteller formula is highlighted as the most common.
- 6Compare results from different formulas.
- 7Note the BSA category (low, average, high).
- 8Review example drug doses for reference.
- 9Consider clinical context for formula selection.
- 10Use results as part of clinical decision-making.
BSA Formulas
Multiple formulas exist for calculating body surface area.
Mosteller Formula (1987)
BSA = √((Height × Weight) / 3600)
- Height in cm, Weight in kg
- Simple, widely used
- Good agreement with other formulas
DuBois Formula (1916)
BSA = 0.007184 × Height^0.725 × Weight^0.425
- Historical gold standard
- Based on direct measurements
- May underestimate in obese patients
Haycock Formula (1978)
BSA = 0.024265 × Height^0.3964 × Weight^0.5378
- Validated for children
- Good across age ranges
- Commonly used in pediatrics
Other Formulas
| Formula | Year | Notes |
|---|---|---|
| Boyd | 1935 | Complex logarithmic |
| Gehan-George | 1970 | Cancer research |
| Fujimoto | 1968 | Japanese population |
Which Formula to Use?
- General use: Mosteller or DuBois
- Pediatrics: Haycock
- Oncology: Often specifies which formula
- Most clinical settings: Mosteller (simplest)
Chemotherapy Dosing
BSA is fundamental to cancer treatment dosing.
Why BSA-Based Dosing?
- Correlates with drug clearance
- Reduces variability in drug exposure
- Established through clinical trials
- Standard practice for most cytotoxic drugs
Common Chemotherapy Doses
| Drug | Typical Dose | Example (BSA 1.8 m²) |
|---|---|---|
| Doxorubicin | 60 mg/m² | 108 mg |
| Paclitaxel | 175 mg/m² | 315 mg |
| Cisplatin | 75 mg/m² | 135 mg |
| Cyclophosphamide | 600 mg/m² | 1080 mg |
| 5-Fluorouracil | 400 mg/m² | 720 mg |
Dose Capping
For very large patients (BSA >2.0 m²):
- Some protocols cap at 2.0 m²
- Prevents excessive toxicity
- Controversial—may reduce efficacy
- Decision is protocol-specific
BSA Limitations in Oncology
- Doesn't account for body composition
- Fat vs. lean mass differences
- Drug-specific considerations
- Increasingly questioned for some drugs
Cardiac Index
BSA normalizes cardiac measurements.
Cardiac Index (CI)
CI = Cardiac Output / BSA
Normal CI: 2.5-4.0 L/min/m²
Why Normalize?
A 5 L/min cardiac output means different things for:
- Small person (BSA 1.5 m²): CI = 3.3 (normal)
- Large person (BSA 2.5 m²): CI = 2.0 (low)
Other Indexed Values
| Parameter | Formula | Normal Range |
|---|---|---|
| Stroke Volume Index | SV/BSA | 30-65 mL/m² |
| Systemic Vascular Resistance Index | SVR × BSA | 1900-2400 |
| Pulmonary Vascular Resistance Index | PVR × BSA | 200-400 |
Clinical Significance
Low cardiac index indicates:
- Heart failure
- Cardiogenic shock
- Need for inotropic support
High cardiac index may indicate:
- Sepsis (hyperdynamic state)
- Hyperthyroidism
- Anemia compensation
Pediatric Applications
BSA is especially important for children.
Why BSA in Pediatrics?
Children vary dramatically in size:
- Weight-based dosing may be inaccurate
- Proportionally larger surface area than adults
- BSA accounts for metabolic differences
Pediatric BSA Formulas
Haycock is often preferred for children: BSA = 0.024265 × Height^0.3964 × Weight^0.5378
Mosteller also validated in children
Age-Based Normal BSA
| Age | Approximate BSA |
|---|---|
| Newborn | 0.2-0.25 m² |
| 1 year | 0.4-0.5 m² |
| 5 years | 0.7-0.8 m² |
| 10 years | 1.0-1.2 m² |
| 15 years | 1.5-1.7 m² |
| Adult | 1.7-2.0 m² |
Special Considerations
- Neonates: Special formulas may apply
- Obese children: Consider ideal body weight
- Growth monitoring: BSA percentiles available
Burn Assessment
BSA is critical in burn injury management.
Rule of Nines (Adults)
Quick estimation of burn surface area:
- Head: 9%
- Each arm: 9%
- Front torso: 18%
- Back torso: 18%
- Each leg: 18%
- Genitals: 1%
Lund-Browder Chart
More accurate, especially for children:
- Adjusts for age-related proportions
- Children have proportionally larger heads
- More precise for fluid calculations
Fluid Resuscitation
Parkland Formula: Fluid = 4 mL × Weight (kg) × % TBSA burned
Example: 70 kg patient with 30% burns = 4 × 70 × 30 = 8,400 mL in first 24 hours
Why BSA Matters
- Total body surface area determines % burned
- % burn determines fluid requirements
- Affects prognosis and treatment decisions
-
20% TBSA requires specialized care
Limitations and Alternatives
When BSA may not be optimal.
Limitations of BSA
Body Composition:
- Doesn't distinguish fat from muscle
- Obese patients: more fat, similar organ size
- Muscular patients may have higher metabolic rate
Extreme Values:
- Very obese: BSA overestimates needs
- Very thin: BSA may underestimate
Disease States:
- Edema affects measurements
- Amputations require adjustment
- Cachexia changes body composition
Alternatives to BSA
Fixed Dosing:
- Some newer drugs use flat doses
- Based on clinical trials showing equivalent safety
Weight-Based:
- mg/kg dosing for some drugs
- Actual vs. ideal vs. adjusted body weight
Pharmacokinetic Dosing:
- Therapeutic drug monitoring
- Individualized based on blood levels
- Carboplatin (AUC-based dosing)
Best Practice
- Follow protocol-specific guidance
- Consider patient factors
- Monitor for toxicity
- Adjust based on response
Pro Tips
- 💡Average adult BSA is approximately 1.7-2.0 m².
- 💡Mosteller formula is simplest: √((height × weight) / 3600).
- 💡Use Haycock formula for pediatric patients.
- 💡Chemotherapy is typically dosed in mg/m² (per BSA).
- 💡Cardiac index = cardiac output / BSA (normal: 2.5-4.0 L/min/m²).
- 💡eGFR is reported per 1.73 m² BSA.
- 💡Different formulas give similar results (within ~10%).
- 💡BSA doesn't account for body composition (fat vs. muscle).
- 💡Some protocols cap BSA at 2.0 m² for dosing.
- 💡Rule of Nines uses BSA for quick burn estimation.
- 💡Children have proportionally larger BSA for their weight.
- 💡Always follow protocol-specific formula requirements.
Frequently Asked Questions
Average adult BSA is approximately 1.7-2.0 m². Men typically have higher BSA (average ~1.9 m²) than women (average ~1.6 m²) due to generally larger body size. BSA varies widely based on height and weight.
