Body Surface Area Calculator
Calculate your body surface area (BSA) in m² using four established medical formulas. Used for chemotherapy dosing, cardiac output, and drug prescribing.
What Is Body Surface Area?
Body surface area (BSA) is the total external surface area of the human body, measured in square metres. It is used extensively in medicine because many physiological parameters — including cardiac output, renal function, and drug metabolism — scale more accurately with BSA than with body weight alone.
BSA is most commonly used to calculate doses for chemotherapy agents, where toxicity and efficacy both correlate with surface area. It is also used to express cardiac index (cardiac output per m² BSA), calculate burn area in trauma patients, and determine appropriate dosing for several other high-risk medications.
The average adult BSA is approximately 1.7–1.9 m². The most widely used formula in clinical practice is the Mosteller formula for its simplicity and accuracy across a wide range of body sizes.
BSA Formulas Compared
| Formula | Year | Equation | Best used for |
|---|---|---|---|
| DuBois & DuBois | 1916 | 0.007184 × H0.725 × W0.425 | Historical standard; adults |
| Mosteller | 1987 | √(H × W / 3600) | Most widely used; easy to calculate |
| Haycock | 1978 | 0.024265 × H0.3964 × W0.5378 | Children and adults |
| Gehan & George | 1970 | 0.0235 × H0.42246 × W0.51456 | Wide range of body sizes |
H = height in cm; W = weight in kg
Worked Examples
Example 1: Average adult male, 178 cm, 80 kg. Mosteller: √(178 × 80 / 3600) = √3.956 = 1.99 m². DuBois: 0.007184 × 1780.725 × 800.425 = 2.00 m². Average BSA ≈ 2.0 m².
Example 2: Adult female, 163 cm, 62 kg. Mosteller: √(163 × 62 / 3600) = √2.808 = 1.68 m². Haycock: 0.024265 × 1630.3964 × 620.5378 = 1.68 m².
Example 3: Child, 120 cm, 22 kg. Mosteller: √(120 × 22 / 3600) = √0.733 = 0.86 m². Haycock (optimised for children): 0.87 m².
Frequently Asked Questions
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Many drugs — particularly chemotherapy agents — have a narrow therapeutic window where the dose needs to be high enough to be effective but not so high as to cause severe toxicity. BSA correlates better with glomerular filtration rate, hepatic blood flow, and plasma volume than body weight alone, making it a more reliable basis for predicting drug distribution and clearance in the body.
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No single formula is definitively superior across all populations. The DuBois formula was the original standard but slightly underestimates BSA in obese patients. The Mosteller formula is widely adopted for its accuracy and simplicity. Haycock is preferred for paediatric patients. For most purposes, the formulas agree within 2–5% of each other.
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The average BSA for adult men is approximately 1.9 m² and for adult women approximately 1.7 m². The range across healthy adults is roughly 1.5–2.3 m². BSA below 1.5 m² (common in small adults and most children) affects drug dosing calculations significantly.
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No. BSA measures the external surface area of the body in square metres. BMI is a ratio of weight to height squared. Body fat percentage is the proportion of total weight that is fat tissue. BSA is a geometric measure; it does not directly reflect body composition. However, taller and heavier people will have higher BSA regardless of how that weight is distributed between muscle and fat.
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This calculator provides estimates based on established formulas and is suitable for educational or general reference purposes. For clinical drug dosing, always use an approved clinical tool and verify the result with a qualified pharmacist or physician. Drug doses based on BSA should never be calculated from a general-purpose web calculator alone.