Du Bois (1916)
Original formula
1.85m²
Scenario
BSA for Children and Infants
Learn how body surface area is calculated for children and infants. Understand pediatric-specific BSA formulas and clinical applications.
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Your Details
cm
kg
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 matters more in pediatrics
BSA-based dosing is especially important in pediatrics because children\'s drug metabolism and distribution differ significantly from adults. Many pediatric medications — including chemotherapy, corticosteroids, and some antibiotics — are dosed per m² of BSA rather than per kg of weight. This provides more consistent drug exposure across children of different ages and sizes.
Pediatric BSA formulas
While the Mosteller formula works for older children and adolescents, several formulas were specifically developed for pediatric use:
- Mosteller: BSA = √(Height × Weight / 3600) — suitable for children over ~2 years
- Haycock: BSA = 0.024265 × Height^0.3964 × Weight^0.5378 — validated for infants and children
- Gehan & George: BSA = 0.0235 × Height^0.42246 × Weight^0.51456 — widely used in pediatric oncology
- Boyd: Considered most accurate for infants and children, but complex to calculate
BSA estimation for infants (without height)
For newborns and young infants where accurate height measurement is difficult, BSA can be estimated from weight alone using standardized tables:
- 3 kg: ~0.25 m²
- 5 kg: ~0.35 m²
- 10 kg: ~0.53 m²
- 15 kg: ~0.70 m²
- 20 kg: ~0.85 m²
- 30 kg: ~1.05 m²
Pediatric clinical applications
- Chemotherapy dosing: Most pediatric oncology drugs are dosed in mg/m²
- Burns assessment: The "rule of nines" and Lund-Browder charts use BSA to estimate burn severity
- Cardiac output calculation: Cardiac index = cardiac output / BSA
- Glomerular filtration rate (GFR): eGFR is normalized to 1.73 m² BSA for comparison across patients
- Caloric requirements: Energy needs are sometimes estimated per m² in critically ill children
FAQ
Frequently Asked Questions
The Mosteller formula works for older children, but specialized formulas (Haycock, Gehan & George) were validated specifically for infants and children and may be more accurate.
Yes. For young infants, BSA can be estimated from weight alone using standardized reference tables. For example, a 5 kg infant has an estimated BSA of approximately 0.35 m².
Children's drug metabolism differs from adults and varies significantly with age and size. BSA-based dosing provides more consistent drug exposure than weight-based dosing across the pediatric population.
The Gehan & George and Mosteller formulas are commonly used in pediatric oncology. The specific formula used depends on institutional protocols and the drug's original dosing studies.
The Lund-Browder chart is the gold standard for pediatric burn assessment. It accounts for the fact that children's body proportions differ from adults (e.g., larger head relative to body).
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