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🧑 Body Surface Area Calculator
Calculate BSA using multiple medical formulas for accurate dosing
📏 Your Measurements
ℹ️ BSA is used in medical settings for drug dosing, cardiac index, and other clinical calculations.
📊 Your Results
Average Body Surface Area
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m² (square meters)
Du Bois Formula
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Mosteller Formula
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Haycock Formula
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Gehan-George Formula
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📚 Understanding Body Surface Area (BSA)
What is Body Surface Area?
Body Surface Area (BSA) is the measured or calculated surface area of a human body. It's expressed in square meters (m²) and is used in many medical settings, particularly for calculating drug dosages, determining cardiac index, and assessing burn severity.
BSA Formulas
This calculator uses four widely accepted formulas:
- Du Bois Formula (1916): BSA = 0.007184 × Height^0.725 × Weight^0.425
The most commonly used formula, considered the gold standard for many years. - Mosteller Formula (1987): BSA = √[(Height × Weight) / 3600]
Simpler calculation, widely used in clinical practice and recommended by many medical organizations. - Haycock Formula (1978): BSA = 0.024265 × Height^0.3964 × Weight^0.5378
Developed specifically for children but also accurate for adults. - Gehan-George Formula (1970): BSA = 0.0235 × Height^0.42246 × Weight^0.51456
Particularly accurate for patients with extreme body weights.
Medical Applications of BSA
- Chemotherapy Dosing: Many cancer drugs are dosed based on BSA to minimize toxicity
- Cardiac Index: Cardiac output divided by BSA gives the cardiac index
- Renal Function: Glomerular filtration rate is often normalized to BSA
- Burn Assessment: Burn severity is calculated as percentage of BSA affected
- Pediatric Dosing: Many pediatric medications are dosed per m² of BSA
- Dialysis: Dialysis adequacy is calculated using BSA
- Transplant Medicine: Organ size matching often considers BSA
Normal BSA Ranges
- Adult Males: Average 1.9 m² (range: 1.6-2.2 m²)
- Adult Females: Average 1.6 m² (range: 1.4-1.8 m²)
- Children: Varies widely with age and size (0.25-1.5 m²)
- Newborns: Approximately 0.25 m²
Factors Affecting BSA
- Height: Taller individuals have greater BSA
- Weight: Heavier individuals have greater BSA
- Body Composition: Muscle vs. fat distribution affects BSA
- Age: BSA increases from birth through adolescence
- Gender: Males typically have larger BSA than females of same height/weight
Clinical Significance
BSA is crucial in medicine because many physiological processes are proportional to body surface area rather than body weight. For example, metabolic rate, cardiac output, and renal function all correlate better with BSA than with body weight alone. This makes BSA-based calculations more accurate for drug dosing and physiological assessments.
Frequently Asked Questions
Which BSA formula is most accurate?
The Mosteller formula is widely considered the most practical and is recommended by many medical organizations. However, all four formulas provide similar results for most adults. The Du Bois formula is the traditional standard, while Haycock is preferred for children and Gehan-George for extreme body weights.
Why is BSA used instead of body weight for drug dosing?
BSA correlates better with many physiological processes than body weight alone. Metabolic rate, cardiac output, and renal function are all proportional to BSA. This makes BSA-based dosing more accurate, especially for chemotherapy and other potent medications where precise dosing is critical.
Can I use BSA for fitness or diet planning?
BSA is primarily a medical measurement. For fitness and diet planning, BMI, body fat percentage, and BMR are more useful metrics. However, BSA can provide insight into your body's metabolic demands and is sometimes used in advanced fitness calculations.
How accurate are BSA calculators?
BSA calculators using established formulas are quite accurate for most people, with an error margin of about 5%. The different formulas typically agree within 0.1 m² for adults. For the most precise measurements, 3D body scanning can be used, but formula-based calculations are sufficient for clinical purposes.
Does BSA change with weight loss or gain?
Yes, BSA changes with weight changes, though not as dramatically as you might expect. A 10 kg weight change typically results in about 0.1-0.15 m² change in BSA. This is why medication dosages may need adjustment after significant weight changes.
Is BSA the same as skin surface area?
Yes, BSA represents the total surface area of the skin covering the body. It's calculated from height and weight because directly measuring skin surface area would be impractical. The formulas provide accurate estimates based on body dimensions.
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