BSA Calculator
Free BSA calculator using the Mosteller formula with metric and imperial units. Calculate body surface area for chemotherapy dosing, burn assessment, and medical applications.
About This Calculator
Body Surface Area (BSA) is the total external surface area of the human body, measured in square meters (m²). It is a critical metric in medicine for calculating chemotherapy drug dosages, administering IV fluids, assessing burn severity, and determining cardiac output indexes. Beyond clinical use, BSA is also relevant for fitness enthusiasts tracking physiological changes and researchers studying metabolic rates.
This calculator uses the Mosteller formula, the most widely adopted method for BSA estimation in clinical practice: BSA (m²) = sqrt( (height (cm) × weight (kg)) / 3600 ). Developed by Dr. Robert Mosteller in 1987 and published in The New England Journal of Medicine, this formula offers an excellent balance of accuracy and simplicity. It is validated for adults, children, and infants.
Our calculator supports both metric (kg/cm) and imperial (lbs/inches) units with automatic conversion. After calculating, you can compare your BSA against reference values: average adult males (1.9 m²), adult females (1.6 m²), children (1.0 m²), and newborns (0.25 m²).
Why BSA Matters in Medicine
BSA is preferred over body weight for drug dosing because it correlates more closely with metabolic rate, cardiac output, and organ function. Two individuals may weigh the same but have very different BSA values due to height differences, leading to different medication requirements. In chemotherapy, doses calculated per m² help ensure therapeutic efficacy while minimizing toxicity. Burn specialists use BSA to estimate the percentage of body surface affected, guiding fluid resuscitation and treatment planning.
Regional Notes
India: Indian patients often have lower average BSA than Western populations. Most Indian hospitals use the Mosteller formula as the standard for chemotherapy dosing and burn assessment.
United States: The Mosteller formula is widely used alongside the Du Bois formula in US clinical practice. BSA-based dosing is standard for chemotherapy and certain antibiotics.
United Kingdom: NHS and UK cancer centers predominantly use the Mosteller formula. BSA is also used in renal function estimation (indexed GFR) and pediatric dosing guidelines.
Features:
- Mosteller formula BSA calculation
- Metric and imperial unit support
- Comparison bar chart vs population averages
- Reference BSA pie chart
- Detailed reference breakdown table
- Shareable URL with saved inputs
Frequently Asked Questions
What is body surface area (BSA)?
Body surface area (BSA) is the total external surface area of the human body measured in square meters. It is widely used in medicine for chemotherapy dosing, IV fluid administration, burn severity assessment, and calculating cardiac output indexes. The Mosteller formula is the most common method: BSA = sqrt((height(cm) x weight(kg)) / 3600).
What is a normal BSA?
Average BSA values: Adult men 1.9 m², Adult women 1.6 m², Children (10 years) 1.0 m², Newborns 0.25 m². Your BSA depends on your height and weight. Athletes and taller individuals typically have higher BSA values.
Why is BSA used for drug dosing instead of weight?
BSA correlates better with metabolic processes than body weight alone because it accounts for both height and weight. Chemotherapy drugs, certain antibiotics, and burn treatments are dosed based on BSA (mg/m²) to provide a more accurate estimate of metabolic mass and body volume, ensuring appropriate therapeutic doses while minimizing toxicity.
What is the Mosteller formula?
The Mosteller formula calculates BSA as the square root of (height in cm multiplied by weight in kg divided by 3600). Published in 1987 in The New England Journal of Medicine, it is the most widely used BSA formula due to its simplicity and accuracy for adults and children.
How is BSA used in chemotherapy dosing?
Chemotherapy drug doses are calculated based on BSA because it provides a more accurate estimate of metabolic mass than body weight alone. Dosage is expressed as mg/m², ensuring patients receive the correct therapeutic dose. A taller or heavier patient requires more drug, and BSA-based dosing accounts for both dimensions.
What is the difference between BSA and BMI?
BMI (Body Mass Index) measures body fat based on height and weight, classifying weight status (underweight, normal, overweight, obese). BSA (Body Surface Area) measures the total surface area of the body in m² and is primarily used for medical dosing, metabolic rate estimation, and burn assessment.
What other BSA formulas exist beyond Mosteller?
Other BSA formulas include the Du Bois formula (1916): BSA = 0.007184 x weight⁰·⁴²⁵ x height⁰·⁷²⁵, Haycock formula, Gehan & George formula, and Fujimoto formula. The Mosteller formula is preferred for its simplicity while maintaining clinical accuracy comparable to these more complex formulas.
Do men and women have different average BSA?
Yes, average BSA differs by gender due to variations in height, weight, and body composition. Adult men average 1.9 m² while adult women average 1.6 m². This difference reflects the generally larger stature and lean body mass of males compared to females.