Du Bois (1916)
Original formula
1.85m²
Scenario
BSA and Creatinine Clearance
Understand how body surface area is used in estimating kidney function. Learn about eGFR normalization to standard BSA.
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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
Why BSA is used in kidney function assessment
Kidney function is measured as glomerular filtration rate (GFR) — the volume of blood filtered by the kidneys per minute. GFR scales with body size: larger people have higher GFR because they have more kidney tissue. To compare kidney function across patients of different sizes, GFR is normalized to a standard BSA of 1.73 m², producing the estimated GFR (eGFR).
How eGFR uses BSA
The Cockcroft-Gault equation estimates creatinine clearance (CrCl), which approximates GFR:
CrCl = [(140 − Age) × Weight (kg)] / [72 × Serum Creatinine (mg/dL)] × 0.85 (if female)
This result is then normalized to standard BSA (1.73 m²):
eGFR = CrCl × (1.73 / Patient\'s BSA)
The eGFR result (in mL/min/1.73m²) allows direct comparison of kidney function regardless of patient size.
CKD staging using eGFR
- Stage 1: eGFR ≥ 90 — normal or high kidney function (with other signs of kidney damage)
- Stage 2: eGFR 60-89 — mildly reduced
- Stage 3a: eGFR 45-59 — mildly to moderately reduced
- Stage 3b: eGFR 30-44 — moderately to severely reduced
- Stage 4: eGFR 15-29 — severely reduced
- Stage 5: eGFR < 15 — kidney failure
BSA in drug dosing for kidney disease
Many medications are cleared by the kidneys and require dose adjustment based on kidney function. The eGFR (normalized to BSA) is used to determine appropriate dosing. For example, many antibiotics have specific dosing recommendations based on eGFR ranges.
Important considerations
- eGFR is an estimate, not a direct measurement. Gold-standard GFR measurement uses inulin or isotopic clearance
- Muscle mass affects serum creatinine — very muscular or very frail patients may have inaccurate eGFR estimates
- The CKD-EPI equation is now preferred over Cockcroft-Gault for eGFR estimation in most clinical settings
- BSA normalization to 1.73 m² is a convention established decades ago and may not perfectly reflect optimal kidney function for all body sizes
FAQ
Frequently Asked Questions
1.73 m² is the average BSA of a "standard adult" established in the 1920s. Normalizing eGFR to this value allows direct comparison of kidney function across patients of different sizes.
Creatinine clearance (CrCl) from the Cockcroft-Gault equation is first calculated using weight, then normalized to standard BSA (1.73 m²) by multiplying CrCl × (1.73 / patient's BSA) to produce eGFR.
eGFR ≥ 90 mL/min/1.73m² is considered normal kidney function. 60-89 is mildly reduced. Below 60 indicates moderate to severe kidney disease, depending on the stage.
Yes. Serum creatinine comes from muscle metabolism. Very muscular people may have higher creatinine and thus lower eGFR despite normal kidney function. Very frail people may have deceptively high eGFR.
It is still widely used for drug dosing decisions, but the CKD-EPI equation is now preferred for diagnosing and staging chronic kidney disease due to better accuracy.
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