Du Bois (1916)
Original formula
1.85m²
Scenario
How Body Surface Area Is Used in Medicine
Explore the five key medical applications of body surface area (BSA), from drug dosing to cardiac assessment.
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Your BSA Results
Mosteller (1987)
Most common
1.84m²
Haycock (1978)
Pediatric use
1.85m²
m²
Average of all three formulas
BSA on Reference Scale
1.85 m²
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Formula Comparison
BSA Reference Range: Average BSA is approximately 1.7 m² for men and 1.6 m² for women. Your average BSA of 1.85 m² is above average, which is common for taller or larger-framed individuals.
The formula
The formula
What BSA Measures
Body Surface Area (BSA) is a measurement of the total external surface area of the human body, expressed in square meters (m²). Unlike BMI, which assesses weight relative to height, BSA estimates the physical extent of the body surface — a metric that correlates closely with metabolic rate, blood volume, and cardiac output.
BSA is most commonly used in clinical medicine to calculate chemotherapy dosages, determine medication doses for drugs with narrow therapeutic windows, and normalize physiological indices such as cardiac index and glomerular filtration rate. Because BSA-based dosing scales drug delivery to a patient's size more precisely than weight alone, it is the standard of care in oncology and several other specialties.
The BSA Formulas
Three validated formulas are provided in this calculator. Each was derived from measurements of different populations, and while they produce similar results for most adults, minor differences are expected. The most widely used formula in current clinical practice is the Mosteller formula, valued for its simplicity.
Du Bois (1916)
BSA = 0.007184 × W0.425 × H0.725
Mosteller (1987)
BSA = √(W × H ÷ 3600)
Haycock (1978)
BSA = 0.024265 × W0.5378 × H0.3964
Where W = weight in kilograms, H = height in centimeters
Formula Source
Du Bois & Du Bois (1916) — A formula to estimate the approximate surface area if height and weight be known. Archives of Internal Medicine, 17, 863–871.
Reference URL: https://doi.org/10.1001/archinte.1916.00080130008002
Mosteller (1987) — Simplified calculation of body-surface area. New England Journal of Medicine, 317(17), 1098.
Reference URL: https://doi.org/10.1056/NEJM198707233170417
Haycock et al. (1978) — Geometric method for measuring body surface area: A height-weight formula validated in infants, children, and adults. The Journal of Pediatrics, 93(1), 62–66.
Last Verified: 2026-08-09
Worked Example
Consider an adult who weighs 70 kg and stands 175 cm tall. Applying each formula side by side:
Du Bois: 0.007184 × 700.425 × 1750.725 = 0.007184 × 6.08 × 42.29 ≈ 1.85 m²
Mosteller: √(70 × 175 ÷ 3600) = √(12,250 ÷ 3600) = √3.403 ≈ 1.84 m²
Haycock: 0.024265 × 700.5378 × 1750.3964 = 0.024265 × 9.82 × 7.75 ≈ 1.85 m²
All three formulas converge near 1.85 m² for this individual, which is a typical adult BSA value. The small variation between formulas (within 0.01 m² in this case) is clinically acceptable for most applications.
BSA Formula Comparison Table
| Formula | Equation | Typical Use Case |
|---|---|---|
| Du Bois (1916) | 0.007184 × W0.425 × H0.725 | Original reference standard; widely cited in research and historical clinical data. |
| Mosteller (1987) | √(W × H ÷ 3600) | Most commonly used in modern clinical practice due to its simplicity and strong agreement with the Du Bois formula. |
| Haycock (1978) | 0.024265 × W0.5378 × H0.3964 | Often preferred for pediatric and neonatal populations; validated across a wider age range including infants. |
Why BSA Alone Is Not a Full Picture
BSA is a powerful clinical tool, but it is not a standalone health assessment. A single BSA value does not reveal whether a person is underweight, overweight, or has a healthy body composition. Two individuals with identical BSA can have very different ratios of muscle to fat, different metabolic rates, and different overall health profiles.
BSA is most useful when applied as part of a broader clinical context — for example, when calculating a chemotherapy dose, the clinician also considers organ function, performance status, and prior treatment response. For general wellness tracking, BSA is less informative than BMI, waist circumference, or body composition measurements.
Known Limitations
- BSA formulas are population-derived estimates, not direct measurements. Actual surface area varies with body shape, posture, and individual anatomy.
- The Du Bois formula was derived from only nine subjects, which limits its statistical generalizability across diverse populations.
- BSA formulas may be less accurate at extremes of height and weight (very tall, very short, underweight, or severely obese individuals).
- BSA does not account for body composition — two people with the same BSA can have very different fat-to-muscle ratios.
- BSA is not a fitness metric. It was designed for medical dosing and physiological normalization, not for tracking weight or health status over time.
Scenario guide
Scenario guide
1. Drug dosing (especially chemotherapy)
BSA is the standard dosing parameter for most chemotherapy agents and many other medications. Drugs are prescribed in mg/m² (milligrams per square meter of BSA). This ensures that patients of different sizes receive proportionally appropriate doses — neither too much nor too little relative to their body size and metabolic capacity.
2. Cardiac output assessment
Cardiac output (total blood pumped by the heart per minute) naturally varies with body size. To compare heart function across patients, cardiac output is divided by BSA to produce the cardiac index (CI = CO / BSA, normal range 2.5-4.0 L/min/m²). This allows clinicians to assess whether a patient\'s heart is functioning appropriately for their body size.
3. Renal function normalization
Estimated glomerular filtration rate (eGFR) is normalized to a standard BSA of 1.73 m² to allow fair comparison of kidney function across patients. Without this normalization, a large person would always appear to have "better" kidney function than a small person, simply because they have more kidney tissue.
4. Burn severity assessment
Burn injuries are classified by the percentage of total BSA affected. The "Rule of Nines" (for adults) divides the body into regions representing multiples of 9% of total BSA. For children, the Lund-Browder chart accounts for age-dependent body proportion differences. Burn severity and fluid resuscitation protocols are based on % BSA burned.
5. Metabolic rate and caloric requirements
Basal metabolic rate (BMR) correlates more closely with BSA than with body weight alone. In clinical nutrition, particularly for critically ill patients, caloric and protein requirements are sometimes estimated per m² of BSA to account for differences in metabolically active tissue.
Summary table
- Drug dosing: mg/m² — chemotherapy, antibiotics, corticosteroids
- Cardiac index: L/min/m² — heart function assessment
- eGFR: mL/min/1.73m² — kidney function comparison
- Burn assessment: % TBSA — injury severity and fluid needs
- Caloric requirements: kcal/m²/day — clinical nutrition
FAQ
Frequently Asked Questions
BSA is used for: drug dosing (especially chemotherapy), cardiac index calculation, eGFR normalization, burn severity assessment, and metabolic rate estimation.
BSA correlates better with cardiac output, renal blood flow, and glomerular filtration rate — all of which influence drug distribution and clearance. Weight alone does not capture these physiological differences.
Cardiac index = cardiac output ÷ BSA (normal: 2.5-4.0 L/min/m²). It normalizes heart pump function for body size, allowing fair comparison across patients of different sizes.
Burn severity is expressed as % of total body surface area (TBSA) burned. The Rule of Nines estimates TBSA for adults; the Lund-Browder chart is used for children. Fluid resuscitation volume is calculated from % TBSA.
Yes, extensively. Pediatric drug dosing, burn assessment, cardiac assessment, and growth monitoring all use BSA. Pediatric-specific BSA formulas (Haycock, Gehan & George) are often preferred over adult formulas.
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