Body Surface Area Calculator

Calculate BSA using multiple validated medical formulas with instant results

🧮 Body Surface Area Calculator

Calculate BSA using multiple validated formulas

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). It is calculated using height and weight measurements and serves as an important biometric parameter in medical practice.

BSA is more accurate than body weight alone for determining metabolic mass because it correlates better with body fat-free mass. This makes it essential for calculating proper medication dosages, especially for chemotherapy drugs, antibiotics, and steroids where precision is critical.

Our calculator uses multiple validated formulas including Mosteller (most popular), Du Bois, Haycock, Gehan & George, Boyd, Fujimoto, Takahira, and Schlich to provide comprehensive BSA estimates for clinical and research applications.

How to Use the BSA Calculator

Select your gender (Male or Female) as some formulas use gender-specific calculations
Enter your body weight in either kilograms or pounds using the dropdown selector
Enter your height either in feet and inches OR in centimeters (the calculator will clear the other field automatically)
Click 'Calculate BSA' to see your results using all available formulas
Review the Mosteller formula result (most commonly used) and compare with other validated formulas

Latest Medical Insights on BSA

Clinical Applications: BSA is crucial for dosing chemotherapy, antibiotics, and steroids; calculating cardiac index and glomerular filtration rate (GFR); fluid resuscitation in burns using the Parkland formula; and assessing metabolic mass more accurately than weight alone.

Mosteller Formula Preference: The Mosteller formula (BSA = √[height(cm) × weight(kg) / 3600]) is the most popular due to its simplicity and accuracy. It's widely used in oncology, pediatrics, and general medical practice for consistent dosing outcomes.

Normal BSA Ranges: Normal adult BSA typically ranges from 1.7-1.9 m², though this varies by age, gender, and body composition. Children and smaller adults will have lower BSA values, while larger individuals may exceed 2.0 m².

BSA-Based Dosing Guidelines: Current medical guidelines prefer BSA-based dosing for chemotherapy to ensure consistent therapeutic outcomes. However, critiques exist for narrow therapeutic index drugs due to individual variability in drug metabolism and distribution.

Measurement Best Practices: Use validated formulas like Mosteller; measure height and weight accurately without rounding intermediate values; round final BSA to the nearest hundredth; consider patient factors (age, gender, obesity); electronic calculators reduce errors versus traditional nomograms.

Understanding BSA Formulas and Applications

Different BSA Formulas

Multiple formulas exist for calculating BSA, each with slightly different mathematical approaches. The Mosteller formula is most commonly used due to its simplicity, while Du Bois is one of the oldest and most validated. Haycock, Gehan & George, and other formulas may be preferred in specific clinical contexts or research settings. Our calculator provides all major formulas so you can compare results.

Clinical Uses of BSA

Chemotherapy Dosing: Most cancer drugs are dosed based on BSA to maintain consistent blood levels and therapeutic effects while minimizing toxicity
Cardiac Index: BSA is used to normalize cardiac output measurements, providing the cardiac index (CI = cardiac output / BSA)
Renal Function: Glomerular filtration rate (GFR) is often normalized to BSA for more accurate kidney function assessment
Burn Treatment: The Parkland formula uses BSA to calculate fluid resuscitation requirements in burn patients
Radiation Therapy: BSA helps determine appropriate radiation doses and treatment planning in oncology

Normal BSA Values

Average adult BSA is approximately 1.7-1.9 m², but this varies significantly based on height, weight, age, and gender. Newborns typically have BSA around 0.25 m², children range from 0.5-1.5 m² depending on age, and larger adults may exceed 2.0-2.5 m². BMI complements but doesn't replace BSA for clinical size estimation.

Frequently Asked Questions

What is the most accurate BSA formula?

The Mosteller formula is considered the most practical and widely accepted due to its simplicity and accuracy. However, all validated formulas (Du Bois, Haycock, etc.) provide clinically acceptable results with only minor variations. The choice often depends on institutional preference and specific clinical context.

Why is BSA important for medication dosing?

BSA provides a more accurate estimate of metabolic mass than weight alone because it correlates better with body fat-free mass and organ size. This is especially critical for chemotherapy drugs and other medications with narrow therapeutic windows, where precise dosing is essential for efficacy and safety.

How does BSA differ from BMI?

BMI (Body Mass Index) is a ratio of weight to height squared used to classify body weight categories (underweight, normal, overweight, obese). BSA measures total body surface area and is used for clinical calculations like drug dosing and cardiac output normalization. They serve different purposes and complement each other in medical assessment.

Can BSA be used for children?

Yes, BSA calculations are commonly used in pediatric medicine, especially for chemotherapy dosing and determining appropriate medication amounts. The same formulas apply, but normal BSA values are much lower for children (typically 0.5-1.5 m² depending on age) compared to adults.

How accurate do my measurements need to be?

For clinical purposes, measure weight to the nearest 0.1 kg (or 0.2 lbs) and height to the nearest 0.5 cm (or 0.25 inches). Avoid rounding intermediate calculation values, but round the final BSA result to the nearest hundredth (two decimal places). Accurate measurements are essential for proper medication dosing.

What if different formulas give different results?

Small variations between formulas (typically within 0.05-0.10 m²) are normal and clinically acceptable. The Mosteller formula is most commonly used in practice. If you see larger discrepancies, double-check your height and weight inputs for accuracy. For critical medical decisions, always consult with healthcare professionals.