Body Surface Area Calculator - Estimate Your BSA Free BSA Calculator
Calculate your body surface area using five scientific formulas. Enter your height and weight in metric or imperial units to estimate BSA instantly.
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Body Surface Area Calculator - Guide
What is Body Surface Area?
Body surface area (BSA) is the measured or calculated total area of the outer surface of the human body. Expressed in square metres (m²), BSA is a key parameter in clinical medicine used for drug dosing (especially chemotherapy), calculating cardiac index, determining burn severity, and estimating renal clearance.
BSA Formulas
Du Bois (1916):
BSA = 0.007184 × H0.725 × W0.425
Mosteller (1987):
BSA = √(H × W / 3600)
Haycock (1978):
BSA = 0.024265 × H0.3964 × W0.5378
Gehan & George (1970):
BSA = 0.0235 × H0.42246 × W0.51456
Boyd (1935):
BSA = 0.0003207 × H0.3 × W(0.7285 − 0.0188 × log10W)
H = height in cm, W = weight in kg (Boyd uses weight in grams internally).
Typical BSA Values
- Newborn: ~0.25 m²
- Child (10 years): ~1.14 m²
- Adult female (average): ~1.6 – 1.8 m²
- Adult male (average): ~1.8 – 2.0 m²
Clinical Uses of BSA
- Drug Dosing: Many drugs, especially chemotherapy agents, are dosed per m² of BSA to account for variations in body size and metabolism.
- Cardiac Index: Cardiac output divided by BSA gives the cardiac index, used to evaluate heart function.
- Burn Assessment: The “Rule of Nines” uses BSA to estimate the percentage of body affected by burns.
- Renal Function: Glomerular filtration rate (GFR) is often normalised to 1.73 m² BSA for comparison across patients.
Which Formula Should I Use?
The Du Bois formula is the most widely used in clinical practice and is the default in most medical references. Mosteller is popular for its simplicity. Haycock is often preferred for paediatric patients. In practice, the differences between formulas are usually small (<5%) for average adults.