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BSA Calculator

Calculate Body Surface Area using Mosteller, Du Bois, and Boyd formulas.

BSA formulas compared

This calculator provides results from all four major BSA formulas so you can compare them and choose the most appropriate one for your clinical context:

  • Mosteller (1987): BSA = √(H × W / 3600) — simple, accurate, most widely used in oncology
  • Du Bois & Du Bois (1916): BSA = 0.007184 × H^0.725 × W^0.425 — oldest formula, based on 9 subjects; still widely cited
  • Haycock (1978): BSA = 0.024265 × H^0.3964 × W^0.5378 — validated for paediatric populations
  • Boyd (1935): BSA = 0.0003207 × H^0.3 × (W×1000)^(0.7285 − 0.0188 log(W×1000)) — preferred for neonates

Clinical applications of BSA

  • Chemotherapy dosing: Most cancer drugs are dosed in mg/m² of BSA. For example, carboplatin is commonly prescribed at 300–450 mg/m².
  • Cardiac index: CI = Cardiac Output (L/min) ÷ BSA (m²). Normal range: 2.5–4.0 L/min/m².
  • Burns assessment: The Rule of Nines estimates the percentage of BSA affected by burns to guide fluid resuscitation.

⚠️ This calculator is for informational purposes only. All medical dosing decisions must be made by qualified healthcare professionals.

Frequently asked questions

What is Body Surface Area (BSA)?
Body Surface Area (BSA) is a measurement of the total surface area of the human body, expressed in square metres (m²). It is more accurate than body weight for many clinical calculations because it better represents metabolic mass and accounts for differences in body composition.
Why is BSA used in medicine?
BSA is widely used for calculating chemotherapy drug doses, where dosing errors can be life-threatening. It is also used for calculating cardiac index (cardiac output normalised to BSA), glomerular filtration rate in paediatrics, caloric requirements, and burn area assessments.
Which BSA formula is most accurate?
The Mosteller formula (1987) is the most commonly used in modern clinical practice due to its simplicity and good accuracy: BSA = √(height × weight / 3600). The Du Bois formula (1916) is older but still widely cited in literature. The Haycock formula is preferred for paediatric patients. The Boyd formula is used for neonates.
What is the average BSA for an adult?
The average BSA for a healthy adult male is approximately 1.9 m² and for an adult female approximately 1.6 m². Paediatric values range from 0.25 m² for neonates to 1.33 m² for 10-year-olds. These values are used as reference standards in drug dosing guidelines.
What is the Mosteller formula?
The Mosteller formula is: BSA (m²) = √(Height (cm) × Weight (kg) / 3600). It is simple, accurate, and widely adopted in oncology protocols. For a person 170 cm tall weighing 70 kg: BSA = √(170 × 70 / 3600) = √3.306 ≈ 1.818 m².

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