What Is Your Body Surface Area?
What is your body surface area?
Body Surface Area Calculator
5 Formulas · Drug Dosing · Rule of Nines · Sensitivity
Results update in real time as you adjust any input.
Common: 75 / 100 / 125 mg/m² · Sets your personal dose row in Dosing tab
Results are estimates only and do not constitute medical advice. Consult a qualified healthcare professional before making health decisions.
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Body Surface Area (BSA) is the measured or calculated surface of a human body in square meters. Unlike body weight, which changes significantly with hydration, fat mass, and muscle mass, body surface area changes more slowly and correlates more reliably with many physiological parameters — including cardiac output, kidney function, and the distribution of certain drugs in the body. BSA is clinically essential for chemotherapy dosing, where many cytotoxic medications are dosed in mg/m² rather than mg/kg. It's also used in burn treatment (the "Rule of Nines" estimates percent of body surface burned), in calculating cardiac index (cardiac output / BSA), and in pediatric drug dosing. For adults, the average BSA is approximately 1.7 m² for females and 1.9 m² for males. Several validated formulas exist for BSA estimation, each calibrated to different populations. The DuBois formula (1916), though the oldest, remains widely used. The Mosteller formula (1987) is simpler to calculate and commonly used in pharmacy. The Haycock formula performs better for children. The Gehan-George formula was derived from a broader dataset. This calculator computes BSA using all four formulas and presents the consensus value — the most reliable approach for most clinical situations.
- →Calculating BSA for chemotherapy dose calculation (mg/m²)
- →Medical education and understanding clinical pharmacokinetics
- →Estimating cardiac index = cardiac output / BSA
- →Understanding body surface relative to metabolic and physiologic parameters
- →Calculating burn percentage when paired with body surface maps
Dr. Patel is preparing a chemotherapy regimen for a patient: female, 5'5", 145 lbs. DuBois formula: BSA = 0.007184 × (65.8 cm^0.725) × (65.8 kg^0.425) = 1.71 m². The planned drug dose is 75 mg/m². Dose = 75 × 1.71 = 128.25 mg, rounded to 130 mg per clinical protocol. The calculator runs all four formulas and shows the consensus BSA for verification.
Why use BSA instead of body weight for drug dosing?
BSA correlates better than body weight with glomerular filtration rate, cardiac output, and the clearance of many drugs. For chemotherapy, where the therapeutic window is narrow (effective dose close to toxic dose), BSA-based dosing reduces variability in drug exposure between patients of different sizes.
What is the most accurate BSA formula?
No single formula is universally most accurate. The DuBois & DuBois formula is historically referenced but was derived from only 9 subjects. Mosteller's formula is commonly used in pharmacy due to its simplicity (√(H × W / 3600)). Haycock performs best in children. For most adult clinical applications, any of the four major formulas gives results within ±5% of each other.
What is the average BSA for adults?
The average BSA for adult females is approximately 1.6-1.7 m² and for adult males approximately 1.9 m². Newborns have BSA of approximately 0.25 m². BSA increases throughout childhood and plateaus in adulthood, changing relatively slowly compared to body weight.
How is BSA used in burn medicine?
Burn care uses BSA to estimate the percentage of the body surface that has been burned (% TBSA — Total Body Surface Area burned). The 'Rule of Nines' divides the adult body into regions each representing 9% (or 18%) of total BSA. Fluid resuscitation protocols (e.g., Parkland formula) use % TBSA burned and body weight to calculate fluid requirements.