Body Surface Area Calculator BSA
Body Surface Area Calculator
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Required for Schlich formula
Current Measurements:
Weight: 70.3 kg (155 lbs)
Height: 175.3 cm (5' 9")
Why BSA Matters
•More accurate than body weight for metabolic mass
•Used for chemotherapy medication dosing
•Calculates cardiac index (heart performance)
•Assesses metabolic rate and energy needs
Enter your measurements to calculate your body surface area
Body Surface Area (BSA) is the total surface area of the human body, measured in square meters. It is used primarily in medicine to calculate drug doses (especially chemotherapy and some cardiovascular medications), assess burn severity, and determine fluid replacement needs. This calculator uses multiple validated formulas to estimate your BSA.
BSA Calculation Formulas
Several formulas are used clinically, each with slightly different accuracy across different body types. The DuBois & DuBois formula is the oldest and most widely used. The Mosteller formula is popular for its simplicity. The Haycock formula is considered most accurate for children and neonates.
Mosteller: BSA = √(Height(cm) × Weight(kg) / 3600) DuBois: BSA = 0.007184 × Height(cm)^0.725 × Weight(kg)^0.425 Haycock: BSA = 0.024265 × Height(cm)^0.3964 × Weight(kg)^0.5378
Average BSA is approximately 1.7-1.9 m² for adults. Men average 1.9 m², women 1.6 m².
Clinical Uses of BSA
BSA-based dosing is used for medications where therapeutic and toxic doses are close together, particularly chemotherapy agents. Using BSA normalizes for body size, helping ensure patients of different sizes receive proportionally appropriate doses. Burn assessment uses BSA to estimate the percentage of skin affected (the Rule of Nines).
Frequently Asked Questions
Why is BSA used instead of body weight for drug dosing?⌄
Body weight alone does not account for the distribution and clearance of drugs across different body compartments. BSA more accurately reflects metabolic mass and kidney filtration capacity for drugs with narrow therapeutic windows. For most common drugs, weight-based dosing is sufficient, but for high-stakes medications like chemotherapy, BSA dosing reduces variability.
Is BSA the same as body fat percentage?⌄
No. BSA is a measure of external surface area in square meters. Body fat percentage is the proportion of your total mass that is fat. They are completely different metrics used for different purposes. BSA increases with height and weight regardless of body composition.
What is the Rule of Nines in burn assessment?⌄
The Rule of Nines divides the body into areas of approximately 9% BSA each to quickly estimate the extent of burns: head and neck (9%), each arm (9%), chest (9%), abdomen (9%), upper back (9%), lower back (9%), each thigh (9%), each lower leg (9%), and genitalia (1%). This helps determine fluid resuscitation needs and burn severity classification.
How accurate are BSA formulas?⌄
BSA formulas have a margin of error of 5-10% compared to direct measurement methods. For most clinical purposes this level of accuracy is acceptable. Direct measurement methods (scanning, surface mapping) are used in specialized research contexts but not in routine clinical practice. Different formulas can give slightly different results for the same person.