Body Surface Area (BSA) Calculator
Enter height (cm) and weight (kg) to estimate body surface area (BSA, m²) using the four most-cited clinical formulas — Mosteller, Du Bois, Haycock and Boyd. BSA is the basis of mg/m² dosing in oncology and many paediatric protocols, and normalises cardiac output (cardiac index) and eGFR. Mosteller is the default because its closed-form sqrt(H × W / 3600) is easy to verify at the bedside.
Enter a valid height (30–250 cm) and weight (1–300 kg).
Estimated BSA
1.82 m²
Mosteller
Average adult range
Between 1.6 and 2.0 m² — close to the typical adult range. Many chemotherapy and cardiac-index protocols normalise to 1.73 m².
Mean of four
1.82 m²
Standard clinical normalisation: BSA = 1.73 m² (used for eGFR and cardiac index).
All four formulas
-
Mosteller
— m²
-
Du Bois
— m²
-
Haycock
— m²
-
Boyd
— m²
Example dose calculation
Total dose = dose-per-m² × BSA — the convention used in oncology and a number of paediatric protocols.
319 mg
For reference only. Actual doses must be set by a clinician based on weight, age, hepatic / renal function and the drug label.
Formula
Mosteller (1987): BSA = √(H × W / 3600) Du Bois (1916): BSA = 0.007184 × W^0.425 × H^0.725 Haycock (1978): BSA = 0.024265 × W^0.5378 × H^0.3964 Boyd (1935): BSA(cm²) = 3.207 × W(g)^(0.7285 − 0.0188·log₁₀W) × H^0.3 (H in cm, W in kg, BSA in m²; Boyd internally treats weight in grams.)
- · Mosteller is the most common clinical / oncology choice — one sqrt() makes it easy to verify at the bedside.
- · Du Bois (1916) is the historical reference. The "standard adult BSA" of 1.73 m² comes from this formula and is the normalisation constant used for eGFR and cardiac index.
- · Haycock (1978) and Boyd (1935) are the most accurate for infants and small children — Haycock is the usual choice for neonatal and paediatric dosing.
- · Healthy adult BSA typically ranges 1.5–2.3 m² (median ≈ 1.9 m² for men, 1.6 m² for women). BSA differs from BMI: BMI measures relative fatness; BSA measures metabolic surface.
- · Some chemotherapy protocols (e.g. carboplatin under the Calvert formula) use actual BSA; others cap BSA at 2.0 m² in obese patients to avoid overdosing. Follow the local protocol or product label.
- · Sources: Mosteller, NEJM 1987; Du Bois & Du Bois, Arch Intern Med 1916; Haycock et al., J Pediatr 1978; Boyd, Univ. of Minnesota Press 1935.
Frequently asked
Which formula do hospitals actually use?
Oncology overwhelmingly uses Mosteller because sqrt(H × W / 3600) is easy to memorise and easy to double-check at the bedside. Du Bois has the longest history in adult medicine, and Haycock is the standard for neonates and small children. The four formulas agree within roughly ±5 %, but for actual dosing you must follow your hospital's SOP — do not switch formulas in clinical practice.
How is BSA different from BMI?
BMI = weight ÷ height² measures relative fatness — whether body weight is high or low for the height. BSA = √(H × W / 3600) measures absolute body size — used as a proxy for metabolic surface area. Two people with the same BMI can have very different BSAs (a tall person vs a short one), and vice versa. Clinically, drug doses, cardiac output and burn-surface estimation use BSA, while overweight / obesity classification uses BMI.
Why is 1.73 m² treated as the "standard"?
1.73 m² is the mean BSA Du Bois reported in 1916. It has since become the normalisation constant in nephrology and cardiology — eGFR is reported as "mL/min/1.73 m²" and cardiac index = cardiac output ÷ BSA is normalised to 1.73 m². The average adult today is larger than in 1916, but the 1.73 m² constant is baked into a century of laboratory reports and clinical literature; changing it would break comparability.
Can I share a specific result?
Yes — height, weight, formula choice and dose-per-m² are all reflected in the URL on every change. Use the "Copy link" button at the bottom-right to share the exact inputs; opening the link reproduces the same BSA, four-formula comparison and example dose.
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