Body surface area (BSA) is one of the most clinically important measurements in medicine. It drives chemotherapy dosing, burn severity assessment, and kidney function normalization.
This article explains the four validated BSA formulas, how they differ, and which one to use in different clinical contexts.
What is Body Surface Area?
Body surface area is the total external surface of the human body, measured in square meters (m²). For an average adult, BSA ranges from ~1.6 m² (women) to ~1.9 m² (men). A newborn has approximately 0.2 m².
Why BSA beats body weight for drug dosing
Two patients can weigh the same but have very different body surface areas depending on their height. BSA-based dosing accounts for this variation, producing more consistent drug concentrations and better clinical outcomes.
The Four Standard Formulas
Several validated formulas exist for calculating BSA. They differ in precision, target population, and clinical adoption.
| Formula | Year | Key Feature |
|---|---|---|
| Du Bois | 1916 | Oldest, most widely used; oncology standard |
| Mosteller | 1987 | Simplest formula; NEJM-endorsed |
| Haycock | 1978 | Best for children and adults; high precision |
| Boyd | 1935 | Non-linear weight relationship; less common |
Du Bois (1916)
The oldest BSA formula, still the most widely used in clinical practice — especially in oncology:
For a 170 cm, 70 kg adult: BSA ≈ 1.81 m².
Mosteller (1987)
The simplest and most practical formula. Published in the New England Journal of Medicine and recommended for clinical use:
Haycock (1978)
Developed and validated for pediatric patients, also highly accurate in adults:
Boyd (1935)
Accounts for a non-linear relationship between weight and BSA. Less commonly used today:
Medical Applications
Chemotherapy Dosing
BSA is the standard basis for chemotherapy dosing. Since many cancer drugs have a narrow therapeutic window — too little fails, too much is toxic — doses are calculated in mg/m² to achieve consistent plasma concentrations across patients.
For example, cisplatin is commonly dosed at 75–100 mg/m² every 3–4 weeks. With a BSA of 1.80 m², that equals 135–180 mg total dose.
Burn Area Assessment
In burn medicine, the percentage of total body surface area (TBSA) burned is estimated using the Rule of Nines: head 9%, each arm 9%, each thigh 9%, each lower leg 9%, front and back trunk 18% each. This percentage drives fluid resuscitation calculations.
Kidney Function (GFR)
Glomerular filtration rate (GFR) is normalized to a standard BSA of 1.73 m². This BSA-adjusted GFR allows clinicians to compare kidney function across patients with different body sizes and make consistent treatment decisions.
Calculate Your Body Surface Area
Compare all four BSA formulas with your own measurements instantly.
Open BSA Calculator →Which Formula Should You Use?
The right formula depends on the clinical context:
- • Oncology / chemo dosing: Du Bois — historical standard, well-validated in this setting.
- • General clinical use: Mosteller — simple and accurate enough for most purposes.
- • Pediatrics: Haycock — developed and validated specifically for children.
- • Research: Report all formulas and acknowledge variability.
For personal health awareness, the choice of formula matters little — differences between formulas are typically less than 2–3%. What matters is knowing your approximate BSA and understanding what it means for your health.