Loading page content...
Reviewed by CalculatorApp.me Health Team
Du Bois, Mosteller, and Haycock formulas, drug dosing, burn assessment, and clinical applications.
1.7 m²
Average adult BSA
Du Bois
Gold-standard formula
mg/m²
Drug dosing unit
9s Rule
Burn area assessment
Free online Body Surface Area (BSA) calculator with Du Bois, Mosteller, Haycock, and Boyd formulas. Used in medical drug dosing and burn assessment.
Enter values above to see results.
Explore our in-depth guides related to this calculator
Expert-reviewed guide to BMI calculation, healthy weight ranges, limitations of BMI, and alternative health metrics. Includes free BMI calculator.
Science-backed guide to sustainable weight loss covering calorie deficits, macronutrients, metabolic adaptation, and free calculators for calories, BMR, and body fat.
Evidence-based guide to calorie counting, macronutrient tracking, TDEE calculation, and using nutrition data to achieve weight loss, maintenance, or muscle gain goals.
Body Surface Area (BSA) is the measured or calculated total area of the external surface of the human body, expressed in square meters (m²). The average adult BSA is approximately 1.7 m² (1.9 m² for males, 1.6 m² for females). BSA is a critical clinical parameter because many physiological processes — metabolic rate, drug clearance, cardiac output, fluid requirements — correlate more closely with surface area than with body weight alone.
BSA cannot be directly measured in clinical practice (unlike weight), so it is always estimated using formulas that take height and weight as inputs. The relationship between BSA and body size follows a power-law curve: BSA scales proportionally to height0.725 × weight0.425 (the Du Bois exponents), meaning taller and heavier individuals have disproportionately more surface area.
The most critical clinical application of BSA is chemotherapy dosing. Since the 1950s, cytotoxic drug doses have been prescribed in mg/m² rather than mg/kg to account for the wide variation in drug clearance between patients of different sizes. BSA-based dosing reduces toxicity without sacrificing efficacy.
BSA = 0.007184 × H^0.725 × W^0.425
Where:
BSA = body surface area (m²)
H = height in centimeters
W = weight in kilograms
Example: 175 cm, 80 kg
BSA = 0.007184 × 175^0.725
× 80^0.425
BSA = 0.007184 × 47.96
× 7.268
BSA = 0.007184 × 348.6
BSA = 1.95 m²
Derived from:
Direct measurement of 9 subjects
Coating method (paper/foil)
Validated over 100+ years
Most widely cited formula
Limitations:
• Only 9 subjects (all adults)
• Less accurate for extremes
(very obese, very small children)
• May underestimate by 3-8%
in obese patientsDespite being over 100 years old and based on only 9 subjects, the Du Bois formula remains the most commonly used BSA formula in clinical practice and drug dosing.
BSA = √(H × W / 3600) Where: H = height in cm W = weight in kg 3600 = constant (60²) Alternative (imperial units): BSA = √(H_in × W_lb / 3131) Example: 175 cm, 80 kg BSA = √(175 × 80 / 3600) BSA = √(14000 / 3600) BSA = √3.889 BSA = 1.97 m² Advantages: ✓ Simple enough for mental calc ✓ Only needs square root ✓ Results within 1-2% of Du Bois ✓ Easy to program/implement Widely used in: • Oncology departments • ICU protocols • Research publications
Mosteller published this as a 'simplified calculation of body-surface area' in the NEJM. Its simplicity made it the preferred formula for rapid clinical calculations.
| Application | How BSA Is Used | Why Not Body Weight | Example |
|---|---|---|---|
| Chemotherapy Dosing | Dose in mg/m² (e.g., 5-FU 400 mg/m²) | Drug clearance correlates with BSA better than weight | BSA 1.8 m² × 400 mg/m² = 720 mg |
| Burn Assessment | Rule of 9s maps body regions to %BSA | Total burn area (%TBSA) guides fluid resuscitation | Parkland: 4 mL × kg × %TBSA (1st 24h) |
| Cardiac Index | CI = Cardiac Output / BSA | Normalizes CO for body size comparison | CI = 5.0 L/min ÷ 1.7 m² = 2.9 L/min/m² |
| GFR Normalization | eGFR standardized to 1.73 m² | Enables comparison across body sizes | GFR × (1.73/patient BSA) |
| Fluid Resuscitation | Maintenance rate linked to BSA | More accurate than weight-based for children | 1500 mL/m²/day maintenance |
| Age Group | Typical BSA (m²) | Height Range | Weight Range | Notes |
|---|---|---|---|---|
| Neonate (term) | 0.20-0.25 | 48-53 cm | 2.5-4.5 kg | Haycock formula preferred |
| Infant (1 yr) | 0.40-0.50 | 72-80 cm | 8-12 kg | Rapid BSA increase in 1st year |
| Child (5 yr) | 0.70-0.80 | 105-115 cm | 17-22 kg | Pediatric dosing critical |
| Adolescent (12 yr) | 1.20-1.40 | 148-160 cm | 38-50 kg | Approaching adult ranges |
| Adult Female | 1.45-1.75 | 155-170 cm |
German physiologist Karl Meeh proposed the first formula relating body surface area to body weight: BSA = k × W^(2/3). The constant k varied by species. This was the first mathematical attempt to estimate BSA but was limited by its single-variable approach — ignoring height.
Delafield Du Bois and his cousin Eugene F. Du Bois measured the surface area of 9 subjects using paper molds. They derived BSA = 0.007184 × H^0.725 × W^0.425 — incorporating both height and weight. Despite the tiny sample, this formula has remained the clinical standard for over a century.
Edith Boyd published an alternative formula using a larger validation cohort. Her formula used a logarithmic weight exponent, making it more complex but slightly more accurate for children. It saw limited clinical adoption due to computational difficulty before calculators.
Oncologists began using mg/m² dosing for cytotoxic drugs after Pinkel showed that drug clearance correlated better with BSA than body weight. This became the standard for cancer treatment and remains the basis for nearly all chemotherapy protocols worldwide.
JCO — Mathijssen et al. (2007)
Systematic review of BSA-based chemotherapy dosing: BSA explains only 15-35% of inter-patient variability in drug clearance. Despite this limitation, no alternative (flat dosing, pharmacogenomics, therapeutic drug monitoring) has consistently proven superior across drug classes. BSA-based dosing remains the pragmatic standard.
NEJM — Mosteller (1987)
Introduced BSA = √(H×W/3600) — a formula accurate to within 1-2% of Du Bois for normal-sized adults. The simplicity enabled widespread adoption. Note: the original NEJM publication was a 1-paragraph letter that became one of the most cited medical formulas.
Burns — Lund-Browder Chart Validation
The Lund-Browder chart provides age-adjusted body region percentages for burn assessment, more accurate than the Rule of 9s for children (where head = 18% at birth vs 9% in adults). TBSA assessment accuracy directly affects fluid resuscitation volumes — critical for burn survival.
Du Bois & Du Bois — Archives (1916)
BSA-based dosing is perfectly accurate for all patients.
BSA explains only 15-35% of inter-patient drug clearance variability. Genetic factors, liver function, kidney function, and drug interactions play major roles. However, BSA is still the best simple metric available — therapeutic drug monitoring can fine-tune individual doses.
Weight-based dosing (mg/kg) is simpler and equally accurate.
Weight-based dosing systematically under-doses obese patients and over-doses small patients. BSA accounts for both height and weight, better reflecting metabolic size. For narrow therapeutic index drugs (chemotherapy), this difference can mean toxicity vs. under-dosing.
The Rule of 9s works for all ages.
The Rule of 9s (head=9%, each arm=9%, each leg=18%, trunk=36%, perineum=1%) is accurate for adults only. In infants, the head is ~18% and legs are ~14% each. The Lund-Browder chart provides age-adjusted percentages and is required for accurate pediatric burn assessment.
Precision health metrics for clinical and personal use — CalculatorApp.me.
Browse Health Calculators →Last updated:
BSA = 0.024265 × H^0.3964 × W^0.5378
Designed for all ages including:
Neonates (premature to term)
Infants and children
Adolescents
Adults
Example: Child — 120 cm, 25 kg
BSA = 0.024265 × 120^0.3964
× 25^0.5378
BSA = 0.024265 × 8.445
× 5.432
BSA = 0.024265 × 45.88
BSA = 0.91 m²
Example: Neonate — 50 cm, 3.5 kg
BSA = 0.024265 × 50^0.3964
× 3.5^0.5378
BSA = 0.024265 × 5.80
× 1.944
BSA = 0.024265 × 11.28
BSA = 0.27 m²
Preferred for:
Pediatric oncology
Neonatal drug dosing
Fluid resuscitationHaycock validated on 81 subjects from birth to adulthood. More accurate than Du Bois for children <30 kg and neonates — essential for pediatric doses where small errors have big consequences.
Gehan & George:
BSA = 0.0235 × H^0.42246
× W^0.51456
Boyd:
BSA = 0.0003207 × H^0.3
× W^(0.7285 − 0.0188×log₁₀(W))
Comparison at 175 cm, 80 kg:
Du Bois: 1.95 m²
Mosteller: 1.97 m²
Haycock: 1.96 m²
Gehan: 1.94 m²
Boyd: 1.96 m²
Differences are typically <3%
for normal-weight adults.
Greater divergence in:
• Morbid obesity (>40 BMI)
• Extreme heights (>200 cm)
• Neonates (<3 kg)
• Cachexia (cancer wasting)
Clinically: most protocols default
to Du Bois or Mosteller unless
the patient is pediatric (→ Haycock)Most BSA formulas agree within 2-3% for normal-sized adults. The choice matters most at the extremes — pediatric, morbidly obese, and cachectic patients.
| Organ Size Indices | LVMI = LV mass/BSA | Detects hypertrophy independent of body size | LVMI >95 g/m² (F) or >115 g/m² (M) |
| 50-75 kg |
| Mean ~1.60 m² |
| Adult Male | 1.70-2.10 | 170-185 cm | 65-95 kg | Mean ~1.90 m² |
| Large Adult | 2.10-2.50 | 185+ cm | 100+ kg | Chemo dose capping may apply |
| Elderly (>70) | 1.40-1.80 | Decreasing | Variable | Sarcopenia reduces BSA |
Haycock, Schwartz, and Wisotsky validated a BSA formula across 81 subjects from neonates to adults. Their formula proved significantly more accurate for children under 10 kg — critical for pediatric oncology and neonatal intensive care where dosing errors can be fatal.
R.D. Mosteller published a radically simplified formula: BSA = √(H×W/3600). Published as a letter in the NEJM, it could be calculated with a basic calculator — democratizing BSA estimation. It agrees with Du Bois within 1-2% for most adults and became the preferred formula in many clinical settings.
Measured 9 individuals by coating them with paper strips, cutting and weighing the paper. Derived the formula BSA = 0.007184 × H^0.725 × W^0.425. Despite the small sample size (criticized ever since), the formula has been validated in thousands of subjects and remains the reference standard.
All BSA formulas give the same result.
For normal-weight adults, formulas agree within 2-3%. But for morbidly obese patients, Du Bois may underestimate by 10-15% vs. Mosteller. For premature neonates, Haycock is significantly more accurate. Formula choice matters at the clinical extremes.