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 used in medicine for calculating chemotherapy drug dosages, IV fluid administration, assessing burn severity, and determining cardiac output indexes. Beyond clinical use, BSA is also relevant for fitness enthusiasts tracking physiological changes and for researchers studying metabolic rates across different body sizes.
This calculator uses the Mosteller formula, the most widely adopted method for BSA estimation in clinical practice worldwide. The formula is: 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 compared to older methods like the Du Bois formula. It is accurate for adults, children, and infants, making it suitable for patients of all ages.
Our calculator supports both metric (kg/cm) and imperial (lbs/inches) units and automatically converts your inputs. After calculating your BSA, you can compare it against reference values for average adult males (1.9 m²), adult females (1.6 m²), children (1.0 m²), and newborns (0.25 m²).
Why BSA Matters
BSA is preferred over body weight for drug dosing because it correlates more closely with metabolic rate, cardiac output, and organ function. A tall, thin person and a short, heavy person may weigh the same but have very different BSA values, leading to different medication requirements. In chemotherapy, doses calculated per m² help ensure that patients receive an appropriate therapeutic dose while minimizing toxicity. Burn specialists also use BSA to estimate the percentage of body surface affected, which guides fluid resuscitation and treatment planning.
Regional Notes
India: Indian patients often have lower average BSA than Western populations due to differences in average height and build. Clinicians should consider population-specific reference ranges when using BSA for drug dosing. Most Indian hospitals use the Mosteller formula as the standard.
United States: The Mosteller formula is widely used in US clinical practice, though some oncology protocols still reference the Du Bois formula. BSA-based dosing is standard for chemotherapy, certain antibiotics, and burn care.
United Kingdom: The NHS and UK cancer centers predominantly use the Mosteller formula. BSA is also used in renal function estimation (e.g., indexed GFR) and in pediatric dosing guidelines.
Features:
- Mosteller formula BSA calculation
- Metric and imperial unit support
- Reference value comparison bar chart
- Reference BSA pie chart for population averages
- Detailed breakdown table
- Shareable URL with saved inputs
Frequently Asked Questions
What is body surface area (BSA)?
Body surface area (BSA) is the total surface area of the human body. It is commonly used in medicine for calculating drug dosages, IV fluids, and burn treatment. 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.
Why is BSA used for drug dosing?
BSA correlates better with metabolic processes than body weight alone. Chemotherapy drugs, certain antibiotics, and burn treatments are dosed based on BSA because it accounts for both height and weight, providing a more accurate estimate of body volume and metabolic capacity.
What is the Mosteller formula for BSA?
The Mosteller formula calculates BSA as the square root of (height in cm multiplied by weight in kg divided by 3600). It is the most widely used BSA formula due to its simplicity and accuracy for adults and children.
How is BSA used in chemotherapy?
Chemotherapy drug doses are often calculated based on BSA because it provides a more accurate estimate of metabolic mass than body weight alone. Dosage is typically expressed as mg/m², ensuring patients receive the correct therapeutic dose based on their body surface area.
What is the difference between BSA and BMI?
BMI (Body Mass Index) measures body fat based on height and weight, while BSA (Body Surface Area) measures the total surface area of the body. BSA is primarily used for medical dosing and metabolic rate estimation, while BMI is used for weight classification.
What is the Dubois formula for BSA?
The Du Bois formula is BSA = 0.007184 x weight(kg)^0.425 x height(cm)^0.725. It was one of the earliest BSA formulas developed in 1916 and is still used in some clinical settings alongside the simpler Mosteller formula.
Do men and women have different average BSA?
Yes, average BSA differs by gender. Adult men typically have a BSA of around 1.9 m², while adult women average 1.6 m². This difference is due to variations in average height, weight, and body composition between genders.