Calculate Your Body Surface Area (BSA) – Du Bois, Mosteller & Haycock
Body Surface Area (BSA) is used in medicine to calculate chemotherapy doses, determine cardiac index, and adjust medication dosing. Measured in m² (square meters). This calculator uses the 3 most widely accepted formulas: Du Bois (1916), Mosteller (1987), and Haycock (1978). The average adult has approximately 1.7 m² of body surface area.
When to use this calculator
- You need to calculate your BSA for a medical dose (chemotherapy, antibiotics).
- You're a healthcare professional adjusting medication based on body surface area.
- You're calculating your cardiac index (cardiac output / BSA).
- You're evaluating renal function corrected for body surface area.
- You want to compare the 3 most commonly used formulas.
Example: 75 kg adult, 175 cm tall
- Mosteller:
√(75 × 175 / 3600)= 1.907 m². - Du Bois:
0.007184 × 75^0.425 × 175^0.725= 1.905 m². - Haycock:
0.024265 × 75^0.5378 × 175^0.3964= 1.909 m². - Average: 1.907 m².
How it works
1 min readThe 3 Formulas
Mosteller (1987) — Most widely used today
BSA (m²) = √(weight(kg) × height(cm) / 3600)Preferred in oncology for its simplicity.
Du Bois & Du Bois (1916) — The original
BSA = 0.007184 × weight^0.425 × height(cm)^0.725Based on only 9 subjects but surprisingly accurate.
Haycock (1978) — Preferred in pediatrics
BSA = 0.024265 × weight^0.5378 × height(cm)^0.3964Validated with a larger sample including children.
Reference values
| Group | Average BSA (m²) |
|---|---|
| Newborn | 0.25 |
| 10-year-old child | 1.14 |
| Adult female | 1.60–1.80 |
| Adult male | 1.80–2.00 |
| Average adult | 1.73 |
Medical applications
Differences between formulas
The 3 formulas yield very similar results for normal-weight adults (difference <2%). Larger differences appear at the extremes: severe obesity, cachexia, or very small children.
Frequently asked questions
Why does body surface area matter in medicine?
Because the dosage of many medications is adjusted based on m² of body surface area, not weight alone. This is more accurate because body surface area correlates better with how the drug is distributed in the body.
Which formula is most accurate?
For adults, all 3 formulas are roughly equivalent. For children, Haycock is preferred. For obesity, none is ideal — some clinics use adjusted weight instead.
How is body surface area used in chemotherapy?
Chemotherapy doses are prescribed in mg/m². For example, if a drug is dosed at 75 mg/m² and your BSA is 1.9 m², your dose is 75 × 1.9 = 142.5 mg.
Does body surface area change when you lose weight?
Yes. If you lose 10 kg, your BSA may decrease by ~0.1 m². In chemotherapy, BSA is recalculated before each treatment cycle.
What is cardiac index and what are normal values?
Cardiac index is cardiac output (liters of blood pumped per minute) divided by your BSA. Normal range: 2.5–4.0 L/min/m². It's measured with an echocardiogram.
Can you calculate body surface area for babies and children?
Yes. The Haycock formula is most accurate for newborns and children. For a 3 kg baby who is 50 cm tall: BSA ≈ 0.20 m².
What is a normal body surface area for adults?
Average adult BSA is about 1.73 m² (range 1.6–2.0 m²). Adult women typically have 1.6–1.8 m², while men are usually 1.8–2.0 m².
Why was the Du Bois formula based on so few people?
The original 1916 Du Bois formula was developed with only 9 subjects, but remarkably, it remains accurate. Modern studies have validated it against larger populations.
Can I use a body composition scale to measure body surface area?
No. Bioimpedance scales measure weight and estimate body composition, but they don't calculate surface area. You need weight + height and a BSA formula.
How often should BSA be recalculated for chemotherapy patients?
BSA should be recalculated before each chemotherapy cycle, as it changes with weight changes. Even small weight losses can affect dosing accuracy.