BSA by the Mosteller formula — weight & height in any unit.
BSA (m²) = √( [Height (cm) × Weight (kg)] / 3600 )
The Mosteller formula is the most commonly used equation for estimating body surface area in clinical settings. It was introduced in 1987 and is favored for its simplicity and reasonable accuracy across diverse patient populations. The formula takes the square root of the product of height (in centimeters) and weight (in kilograms), divided by 3600.
The result is expressed in square meters (m²). This formula closely agrees with more complex methods and is recommended by many oncology and pharmacology guidelines for calculating drug doses.
BSA = √( [180 × 80] / 3600 ) = √( 14400 / 3600 ) = √4.0 = 2.00 m²
Result: BSA = 2.00 m²
A BSA of 2.00 m² is slightly above the commonly cited average for adult males (~1.9 m²), which makes sense for someone who is 180 cm tall and weighs 80 kg — a moderately tall, healthy-weight adult. In clinical practice, a BSA of 2.00 m² would be used to calculate weight-adjusted drug doses, particularly in oncology (e.g., chemotherapy agents dosed in mg/m²). Higher BSA generally means higher absolute doses are prescribed, while lower BSA — typical in children or smaller adults — results in proportionally lower doses. Always consult a qualified healthcare professional before applying BSA to any medical decision.
Body Surface Area (BSA) is the total external surface of the human body. Unlike body weight alone, BSA correlates more reliably with many physiological parameters — including blood volume, cardiac output, and metabolic rate — making it a preferred reference for dosing medications that have a narrow therapeutic window.
Drug Dosing (especially oncology): Many chemotherapy drugs, such as cisplatin and doxorubicin, are dosed in milligrams per square meter of BSA (mg/m²). This approach normalizes dosage across body sizes and helps avoid toxicity in smaller patients or underdosing in larger ones.
Burn Assessment: In burn medicine, clinicians use BSA to estimate what percentage of total body surface area (TBSA) has been burned. This directly determines fluid resuscitation volume (Parkland formula) and prognosis.
Cardiac Physiology: Cardiac index (cardiac output normalized to BSA) helps physicians assess heart function independent of body size.
Renal Dosing: Adjusted GFR (glomerular filtration rate) is sometimes normalized to 1.73 m² BSA — the historical average — allowing comparison across patients of different sizes.
Several BSA formulas exist. The most commonly used include:
| Formula | Year | Equation | |---|---|---| | Mosteller | 1987 | √([H × W] / 3600) | | DuBois & DuBois | 1916 | 0.007184 × H^0.725 × W^0.425 | | Haycock | 1978 | 0.024265 × H^0.3964 × W^0.5378 | | Boyd | 1935 | 0.0003207 × H^0.3 × W^(0.7285−0.0188 × log W) |
The Mosteller formula is preferred in most modern clinical guidelines due to its simplicity, ease of mental calculation, and close agreement with the DuBois standard across typical adult weight ranges.
BSA is an estimate, not a direct measurement. It does not account for body composition (fat vs. muscle), and formulas can lose accuracy at extreme body weights. Some researchers argue that actual body weight or lean body weight may be more appropriate references for specific drugs in obese patients.
⚠️ Disclaimer: This calculator is provided for educational and informational purposes only. It is not intended as medical advice and should not be used to make clinical decisions. Always consult a licensed healthcare provider for medical dosing and treatment decisions.
Using the 'Rule of Nines' in burn medicine: the head and neck account for 9% of BSA, each arm 9%, the chest 18% (front and back), the abdomen 18%, each leg 18%, and the perineum 1%. These proportions differ slightly in children.
Yes — BSA represents the total external skin surface of the body. It is the area that would be measured if you could unfold and lay flat all the skin covering the body. For the average adult, this is roughly 1.7–2.0 m².
In burn medicine, clinicians estimate the percentage of total BSA that has been burned (% TBSA). This figure is used in the Parkland formula — 4 mL × weight (kg) × % TBSA burned — to calculate IV fluid resuscitation needs in the first 24 hours.
Yes. At very high BMI values, BSA formulas may overestimate or underestimate actual surface area because they assume proportional body geometry. Some oncology centers use capped or adjusted BSA values for obese patients, though this practice varies by institution and drug.
BMI (Body Mass Index) = weight(kg) / height(m)² and is used to classify weight status (underweight, normal, overweight, obese). BSA estimates total body skin surface area in m² and is used in clinical dosing and physiology. They measure entirely different things.
The average BSA for an adult male is approximately 1.9 m², and for an adult female approximately 1.6 m². These figures are commonly cited reference values in pharmacology and physiology, though individual BSA varies significantly with height and weight.
This calculator uses the **Mosteller formula**: BSA = √([Height(cm) × Weight(kg)] / 3600). It is the most widely adopted formula in current clinical practice due to its simplicity and accuracy across typical adult body sizes.
The Mosteller formula can estimate BSA for children, but pediatric drug dosing involves additional considerations beyond BSA alone. Always consult a pediatric pharmacist or physician before applying any BSA-based dose to a child.
The Mosteller formula is considered clinically accurate for most adult patients, typically agreeing with direct measurements and the DuBois standard within 2–5%. It may be less accurate at extreme body weights (morbid obesity or severe underweight).
BSA correlates more consistently with blood volume, organ size, and metabolic rate across different body sizes than weight alone. For drugs with a narrow therapeutic index — especially chemotherapy agents — BSA-based dosing reduces the risk of overdose toxicity or underdosing.
To convert height: multiply total inches by 2.54 (e.g., 5 ft 8 in = 68 in × 2.54 = 172.72 cm). To convert weight: divide pounds by 2.2046 (e.g., 150 lb ÷ 2.2046 ≈ 68.04 kg).
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