Body Surface Area (BSA) Calculator

Body Surface Area (BSA) Calculator – Medical & Fitness Use

The Body Surface Area (BSA) Calculator estimates the total external surface area of the human body using the Mosteller formula. BSA is widely used in medicine, clinical research, pharmacology, and advanced fitness analysis because it scales physiological processes more accurately than body weight alone.

BSA calculations are commonly referenced in medical practice and align with guidance used in hospitals and research institutions worldwide, including standards influenced by organizations such as the World Health Organization (WHO) for physiological assessment and dosing normalization.

What Is Body Surface Area (BSA)?

Body Surface Area represents the total outer surface of the human body, expressed in square meters (m²). Unlike body weight or BMI, BSA accounts for both height and weight simultaneously, making it more suitable for scaling biological processes.

Because many physiological functions—such as heat exchange, blood volume, kidney filtration, and drug metabolism—correlate better with surface area than with mass, BSA is often preferred in clinical calculations.

• Used for chemotherapy and medication dosing
• Applied in cardiology and nephrology assessments
• Helpful in metabolic and nutritional research
• Used in advanced fitness and body composition analysis

The Mosteller Formula Explained

This calculator uses the Mosteller formula, one of the most widely accepted and clinically practical equations for estimating BSA. It balances simplicity with accuracy and is commonly used in hospitals and research settings.

BSA (m²) = √[(Height in cm × Weight in kg) ÷ 3600]

The Mosteller formula performs comparably to more complex equations while remaining easy to calculate and interpret. For this reason, it is often the default choice in clinical guidelines and electronic medical systems.

Body Surface Area Calculation Example

Example: A person weighs 70 kg and is 175 cm tall.

BSA = √[(175 × 70) ÷ 3600] ≈ √(3.40) ≈ 1.845 m²

This value may then be used to estimate medication dosages, assess metabolic scaling, or compare physiological parameters across individuals.

Why BSA Is Important in Medicine

Many medications—especially chemotherapy drugs—are dosed based on BSA rather than body weight. This approach helps reduce toxicity and improve treatment consistency across patients of different body sizes.

BSA is also used in cardiology to index cardiac output, in nephrology to normalize kidney function values, and in pediatrics to scale physiological measurements appropriately as children grow.

BSA in Fitness, Nutrition, and Physiology

Outside clinical medicine, BSA is sometimes used in advanced fitness and physiology analysis. Trainers and researchers may use BSA alongside lean body mass, body fat percentage, and basal metabolic rate to understand how body size affects energy expenditure and heat dissipation.

While BSA is not commonly used in everyday fitness tracking, it becomes valuable when analyzing endurance performance, thermoregulation, and comparative physiology across individuals.

Who Should Use the BSA Calculator?

This Body Surface Area Calculator is useful for:

• Medical and nursing students learning dosage calculations
• Healthcare professionals needing quick BSA estimates
• Researchers comparing physiological scaling
• Advanced fitness enthusiasts analyzing body metrics
• Anyone seeking a private, instant BSA calculation

Accuracy and Limitations of BSA Calculations

Body surface area formulas provide estimates, not exact measurements. While the Mosteller formula is widely accepted, different equations may yield slightly different values.

• BSA does not account for body composition differences
• Extremely short or tall individuals may see variability
• Hydration status and posture affect height measurements
• Not intended to replace clinical judgment

For medical decisions, BSA values should always be interpreted by qualified healthcare professionals.

Privacy and Data Handling

This calculator runs entirely in your browser. No personal data is stored, transmitted, or shared. You can use the tool safely and privately at any time.