Use our Body Surface Area Calculator to estimate your BSA for medical dosing and health assessments. Accurate, easy-to-use, and essential for healthcare planning.
Body Surface Area (BSA) is a crucial measurement used in medical settings to determine medication dosages, assess metabolic rates, and evaluate overall health parameters. Our comprehensive Body Surface Area Calculator provides accurate BSA calculations using multiple validated formulas, helping healthcare professionals and individuals obtain precise measurements for various medical applications.
Whether you’re calculating BSA for medication dosing, chemotherapy protocols, or clinical research, understanding this important metric can significantly impact treatment efficacy and patient outcomes. This guide explains everything you need to know about body surface area calculation and provides a user-friendly calculator tool.
Interactive Body Surface Area Calculator
Use our calculator below to quickly determine your body surface area using different formulas. Simply enter your height and weight, select your preferred measurement system and formula, then click “Calculate” to see your results.
BSA Calculator Tool
Medical Disclaimer: This calculator is provided for educational purposes only and is not intended to replace professional medical advice. Always consult with a healthcare provider for proper medical guidance and treatment decisions.
Understanding Body Surface Area
Body Surface Area (BSA) represents the total surface area of the human body expressed in square meters (m²) or square feet (ft²). Unlike simple weight measurements, BSA provides a more accurate representation of metabolic mass and physiological parameters, making it invaluable in clinical settings.
Why BSA Matters
BSA is considered more reliable than body weight alone for many medical calculations because it better correlates with vital physiological functions like cardiac output, blood volume, and metabolic rate. This makes BSA particularly useful for:
- Determining drug dosages, especially for medications with narrow therapeutic windows
- Calculating chemotherapy protocols
- Assessing burn severity and treatment
- Evaluating cardiac function (cardiac index)
- Normalizing physiological parameters across different body sizes
Average BSA Values
| Age Group | Average BSA (m²) | Average BSA (ft²) |
| Newborn | 0.25 | 2.69 |
| Two-year-old child | 0.5 | 5.38 |
| Ten-year-old child | 1.14 | 12.27 |
| Adult female | 1.6 | 17.22 |
| Adult male | 1.9 | 20.45 |
BSA Calculation Methods and Formulas
Several formulas have been developed to estimate body surface area. Each uses different mathematical approaches and may be more suitable for specific populations or clinical scenarios. Our Body Surface Area Calculator includes the most widely validated formulas.
Du Bois Formula
Developed in 1916, the Du Bois formula remains one of the most widely used BSA calculation methods in clinical practice. It works well for both obese and non-obese patients.
BSA = 0.007184 × Weight0.425 × Height0.725
To calculate manually:
- Measure weight in kilograms
- Measure height in centimeters
- Raise weight to the power of 0.425
- Raise height to the power of 0.725
- Multiply these values with 0.007184
Example: For a person weighing 70 kg and 170 cm tall:
BSA = 0.007184 × 700.425 × 1700.725 = 0.007184 × 6.43 × 42.2 = 1.83 m²
Mosteller Formula
Developed in 1987, the Mosteller formula is valued for its simplicity and accuracy. It’s easier to calculate manually than other formulas.
BSA = √(Height × Weight / 3600)
Example: For a person weighing 70 kg and 170 cm tall:
BSA = √(170 × 70 / 3600) = √(11900 / 3600) = √3.31 = 1.82 m²
Haycock Formula
The Haycock formula (1978) is particularly useful for calculating BSA in children and infants, though it works well across all age groups.
BSA = 0.024265 × Weight0.5378 × Height0.3964
Example: For a child weighing 20 kg and 110 cm tall:
BSA = 0.024265 × 200.5378 × 1100.3964 = 0.78 m²
Gehan & George Formula
This formula provides another alternative approach to BSA calculation and is used in some clinical settings.
BSA = 0.0235 × Weight0.51456 × Height0.42246
Example: For a person weighing 70 kg and 170 cm tall:
BSA = 0.0235 × 700.51456 × 1700.42246 = 1.81 m²
Additional BSA Formulas
Several other formulas have been developed for specific populations or clinical contexts:
| Formula | Equation | Best Application |
| Fujimoto | BSA = 0.008883 × Weight0.444 × Height0.663 | Developed for Asian populations |
| Boyd | BSA = 0.0333 × Weight(0.6157 – 0.0188 × log₁₀Weight) × Height0.3 | Works well across wide weight ranges |
| Schlich | Men: BSA = 0.000579479 × Weight × Height Women: BSA = 0.000975482 × Weight × Height |
Gender-specific calculations |
Clinical Applications of BSA
Body surface area calculations have numerous important applications in clinical medicine and research. Understanding when and how BSA is used can help both healthcare professionals and patients appreciate its significance.
Medication Dosing
BSA-based dosing is particularly important for medications with narrow therapeutic windows, where the difference between effective and toxic doses is small. This approach helps standardize dosing across patients of different sizes.
Chemotherapy Dosing
Perhaps the most common application of BSA is in oncology, where chemotherapy agents are typically dosed according to body surface area. This helps balance efficacy against potential toxicity, though some argue that more personalized approaches may be needed for certain medications.
Dose (mg) = BSA (m²) × Dose per unit BSA (mg/m²)
Burn Assessment
In burn care, BSA helps determine the percentage of body affected by burns using tools like the “Rule of Nines” or Lund-Browder charts. This assessment is crucial for fluid resuscitation, nutritional support, and overall treatment planning.
Cardiac Function
Cardiac output and other hemodynamic parameters are often indexed to BSA to create the cardiac index. This allows for more meaningful comparisons between patients of different sizes.
Cardiac Index = Cardiac Output / BSA
Normal cardiac index values range from 2.5 to 4.0 L/min/m², regardless of body size.
Renal Function
Glomerular filtration rate (GFR) is often normalized to BSA, allowing for standardized assessment of kidney function across patients of different sizes.
The standard reference for GFR is approximately 125 mL/min/1.73m² in young adult men and 110 mL/min/1.73m² in young adult women.
Best Practices for Accurate BSA Calculation
Recommended Practices
- Use accurate height and weight measurements taken with calibrated equipment
- Select the appropriate formula based on patient population (adults, children, specific ethnic groups)
- Recalculate BSA when significant weight changes occur
- Use consistent units (metric is preferred in clinical settings)
- Document which formula was used for future reference
- Consider using multiple formulas for verification in critical dosing situations
Practices to Avoid
- Relying on self-reported height and weight
- Using outdated or inappropriate formulas for specific populations
- Failing to recalculate BSA after significant weight changes
- Mixing measurement systems (metric and imperial) without proper conversion
- Using BSA alone for medications with pharmacokinetic complexities
- Overlooking extremes of height and weight where formulas may be less accurate
When should I use BSA instead of body weight for dosing?
BSA is typically preferred for medications with narrow therapeutic windows, particularly chemotherapy agents. It’s also useful when a medication’s pharmacokinetics correlate better with metabolic rate than with simple body weight. However, specific medications may have established protocols that should be followed.
Which BSA formula is most accurate?
No single formula is universally “most accurate” across all populations. The Du Bois formula remains widely used, while the Mosteller formula offers a good balance of simplicity and accuracy. The Haycock formula may be preferred for pediatric patients. In critical dosing situations, consulting with clinical pharmacists or specialists is recommended.
How often should BSA be recalculated?
BSA should be recalculated whenever significant changes in weight occur (typically >10% change). For growing children, regular recalculation is important. For adults on long-term medication regimens dosed by BSA, periodic reassessment is recommended, particularly if weight fluctuations are observed.
Limitations of BSA Calculations
While body surface area calculations are valuable clinical tools, they do have important limitations that should be considered:
- Extremes of body size: Most BSA formulas become less accurate at extremes of height and weight, particularly in severely obese patients
- Body composition variations: BSA doesn’t account for differences in body composition (muscle vs. fat ratio)
- Age-related differences: Some formulas may not adequately address age-related physiological changes
- Ethnic variations: Most widely-used formulas were developed in Western populations and may not be optimal for all ethnic groups
Important Note: While BSA calculations are valuable tools, they should be used as part of a comprehensive clinical assessment. Individual patient factors, organ function, comorbidities, and medication-specific considerations should always be taken into account when making treatment decisions.
Benefits of Online BSA Calculators
Online Body Surface Area calculators offer several advantages over manual calculations:
Accuracy
Digital calculators eliminate human error in complex mathematical calculations, particularly when using formulas with exponents and multiple steps.
Efficiency
Online tools provide instant results, saving valuable time in clinical settings where rapid decisions may be needed.
Formula Comparison
Many online calculators allow users to compare results from different formulas, helping identify potential discrepancies and select the most appropriate approach.
Conclusion: The Importance of Accurate BSA Calculation
Body Surface Area calculation remains a cornerstone of many clinical practices, particularly in medication dosing, burn assessment, and physiological measurements. While various formulas exist, each with its own strengths and limitations, the consistent and accurate application of BSA calculations can significantly improve patient care and treatment outcomes.
Our interactive Body Surface Area Calculator provides a convenient tool for healthcare professionals and individuals to perform quick, accurate BSA calculations using multiple validated formulas. However, it’s important to remember that these calculations should always be used in conjunction with professional medical judgment and comprehensive patient assessment.
Calculate Your Body Surface Area Now
Use our interactive calculator above to determine your BSA using multiple validated formulas. For medical applications, always consult with a healthcare professional.
Medical Disclaimer: The Body Surface Area Calculator provided on this page is intended for educational and informational purposes only. It should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or treatment decisions. Never disregard professional medical advice or delay seeking it because of information provided by this calculator.
