Body Surface Area Calculator - Calculate Your BSA

Calculate your Body Surface Area (BSA) using multiple validated formulas including DuBois, Mosteller, Boyd, and Haycock methods. Essential for medical dosing, drug calculations, and clinical assessments. Get accurate BSA measurements for healthcare and research purposes.

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Height

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Weight

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Calculation Method

Formula Comparison

Enter your height and weight to calculate BSA

Clinical Applications

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Last updated: November 2 2025

Curated by the QuickTooly Team

Related Medical Assessment & Body Measurement Calculators

Comprehensive medical evaluation with these specialized body surface area analysis and clinical assessment tools.

Body Measurement & Medical Assessment

BMI Calculator Compare BMI with BSA for comprehensive body size assessment. Both metrics provide different clinical insights.
Body Fat Calculator Analyze body composition alongside surface area measurements. Understand tissue distribution affecting BSA accuracy.
Ponderal Index Calculator Calculate body density relative to BSA measurements. Assess three-dimensional body proportions for medical use.
Lean Body Mass Calculator Calculate muscle mass relative to body surface area. Important for medication dosing and metabolic assessments.

Metabolic & Physiological Analysis

BMR Calculator Compare metabolic rate with body surface area. BSA correlates with heat production and energy expenditure.
TDEE Calculator Calculate total energy expenditure relative to BSA. Larger surface area affects heat loss and caloric needs.
Water Intake Calculator Calculate hydration needs based on body surface area. BSA affects fluid requirements and medication dilution.
Daily Calorie Calculator Plan nutrition considering BSA impact on metabolic demands. Surface area influences heat regulation and energy needs.

Health Monitoring & Clinical Applications

Diabetes Risk Calculator Assess metabolic health risk relative to body size. BSA helps standardize health metrics across body types.
Cholesterol Ratio Calculator Monitor cardiovascular health indexed to body surface area. Standardize cardiac risk assessment by body size.
Ideal Weight Calculator Determine optimal weight considering body surface area. Target healthy proportions for medical assessments.
Body Shape Calculator Analyze body geometry affecting surface area calculations. Different body shapes impact BSA accuracy and applications.

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What is Body Surface Area (BSA)?

Body Surface Area (BSA) is a measurement of the total surface area of the human body, expressed in square meters (m²). BSA is a more accurate indicator of metabolic mass than body weight alone, making it essential for calculating drug dosages, assessing cardiac function, and determining appropriate medical treatments. Unlike BMI, which only considers height and weight relationships, BSA provides a three-dimensional assessment that better reflects physiological processes.

Medical professionals rely on BSA calculations because many physiological functions, such as cardiac output, glomerular filtration rate, and metabolic rate, correlate more closely with surface area than with body weight. This correlation makes BSA particularly valuable for medication dosing in chemotherapy, determining fluid requirements, and assessing organ function relative to body size.

Understanding Different BSA Calculation Methods

Mosteller Formula (Recommended): BSA = √[(Height × Weight) ÷ 3600]. Introduced in 1987, this simplified formula is the most widely used in clinical practice due to its ease of calculation and high accuracy. It's particularly favored for its practicality in everyday medical settings.
DuBois & DuBois Formula: BSA = 0.007184 × Weight^0.425 × Height^0.725. The original BSA formula from 1916, based on measurements of nine subjects. Despite being over 100 years old, it remains highly accurate and serves as the reference standard for other formulas.
Haycock Formula: BSA = 0.024265 × Weight^0.5378 × Height^0.3964. Developed in 1978 specifically for pediatric patients, this formula provides better accuracy for children and infants, making it preferred in pediatric medicine.
Boyd Formula: BSA = 0.0333 × Weight^(0.6157 - 0.0188 × log10(Weight)) × Height^0.3. A more complex formula that adjusts the weight exponent based on the actual weight value, potentially offering higher precision for extreme body weights.

Clinical Applications of BSA in Healthcare

BSA calculations are fundamental to numerous medical applications, ensuring safer and more effective treatments across various specialties:

Chemotherapy Dosing: Cancer medications are almost universally dosed based on BSA (mg/m²) because this approach better predicts both efficacy and toxicity compared to weight-based dosing. Proper BSA calculation is critical for maximizing treatment effectiveness while minimizing dangerous side effects.
Cardiac Assessment: Cardiac index, the measure of heart performance adjusted for body size, is calculated as cardiac output divided by BSA. Normal cardiac index ranges from 2.5-4.0 L/min/m², providing crucial information about heart function.
Renal Function: Glomerular filtration rate (GFR) is often reported per 1.73 m² of BSA to standardize kidney function assessment across patients of different sizes. This standardization allows for better comparison and tracking of kidney health.
Burn Treatment: BSA is essential for calculating the extent of burn injuries using the "Rule of Nines" and determining appropriate fluid resuscitation volumes. Accurate BSA measurement can be life-saving in severe burn cases.
Pediatric Medicine: Children's medication doses are frequently calculated using BSA rather than weight alone, as it better accounts for developmental differences in drug metabolism and distribution. This approach reduces the risk of under- or over-dosing.

How to Use the BSA Calculator Effectively

Follow these guidelines to ensure accurate BSA calculations and interpretation:

Accurate Measurements: Use precise height and weight measurements taken under standard conditions. Height should be measured without shoes, and weight should be taken in light clothing. For clinical applications, measurements should be as recent as possible.
Choose the Right Formula: Select the Mosteller formula for general adult use, Haycock for pediatric patients, or DuBois for research applications requiring the highest precision. Consider the specific requirements of your intended use.
Unit Conversions: Ensure proper unit conversions when using different measurement systems. Our calculator handles conversions automatically, but always double-check your inputs for accuracy.
Clinical Context: Remember that BSA is one factor among many in medical decision-making. Always consider patient-specific factors such as age, organ function, comorbidities, and individual response patterns.
Professional Consultation: Never use BSA calculations alone for medication dosing or treatment decisions. Always consult with healthcare professionals who can interpret results within the full clinical context.

BSA Normal Ranges and Clinical Interpretation

Adult Reference Ranges

Typical adult BSA ranges from 1.5-2.5 m², with most healthy adults falling between 1.7-2.2 m². Values below 1.5 m² or above 2.5 m² may indicate extreme body sizes that require special consideration in clinical management. These ranges serve as general guidelines, with individual variation expected.

Pediatric Considerations

Children's BSA changes rapidly with growth. Newborns typically have BSA around 0.2-0.3 m², reaching adult ranges by late adolescence. Pediatric BSA calculations are particularly important because children's drug metabolism and physiological responses differ significantly from adults.

Special Populations

Obesity, muscle wasting conditions, edema, and amputation can affect BSA calculations and their clinical interpretation. Healthcare providers may need to adjust dosing strategies or use alternative methods in these situations. Always inform your healthcare team about any conditions that might affect body composition.

Limitations and Important Considerations

Formula Variations: Different formulas can yield results varying by 5-15%, which may be clinically significant for certain medications. Understanding which formula is being used is important for consistent clinical care.
Individual Physiology: BSA calculations assume normal body composition and proportions. Conditions affecting body composition (obesity, muscle wasting, edema) may reduce the accuracy of BSA-based dosing strategies.
Age-Related Changes: As people age, body composition changes can affect the relationship between BSA and physiological function. Elderly patients may require dosing adjustments beyond simple BSA calculations.
Population Differences: BSA formulas were developed primarily using data from Caucasian populations. Some studies suggest that ethnicity-specific adjustments may improve accuracy for certain populations.
Clinical Judgment: BSA should never be the sole factor in medical decision-making. Healthcare providers must always consider the complete clinical picture, including organ function, drug interactions, and patient-specific factors.

Frequently Asked Questions About BSA

Is BSA more accurate than BMI for health assessment?

BSA and BMI serve different purposes. BMI evaluates weight status relative to height for assessing obesity-related health risks, while BSA estimates total body surface area for medical dosing and physiological assessments. Neither alone provides a complete health picture.

How often should BSA be recalculated?

For stable adult patients, BSA changes slowly with weight changes. Recalculate when weight changes by more than 10% or at least annually. For pediatric patients or those with changing medical conditions, more frequent calculations may be needed.

Can I use BSA for fitness or nutrition planning?

While BSA can provide insights into metabolic demands, it's primarily designed for medical applications. For fitness and nutrition, consult with qualified professionals who can consider additional factors like activity level, body composition, and individual goals.

What if my BSA seems unusually high or low?

Extreme BSA values may reflect your natural body proportions or could indicate measurement errors. Double-check your height and weight measurements first. If values seem accurate but extreme, discuss with a healthcare provider for proper interpretation and any necessary adjustments to medical care.

Are there alternatives to BSA for drug dosing?

Yes, some medications use weight-based dosing, fixed dosing, or other methods. The choice depends on the specific drug's pharmacokinetics and clinical evidence. Healthcare providers select the most appropriate method based on established guidelines and individual patient factors.

Medical Disclaimer

This BSA calculator is for educational and informational purposes only and should not replace professional medical advice, diagnosis, or treatment. BSA calculations are estimates that may vary between formulas and should never be used independently for medication dosing or treatment decisions. Always consult qualified healthcare providers regarding medical calculations, drug dosing, or treatment planning. Individual patient factors, medical conditions, and clinical judgment must always be considered alongside BSA calculations. This tool is not intended for emergency medical situations or as a substitute for professional medical care.