Du Bois Body Surface Area (BSA) Calculator
Use this calculator to estimate body surface area using the classic Du Bois formula. Choose metric or imperial units, enter your values, and click calculate.
What is BSA and why does it matter?
Body Surface Area (BSA) is an estimate of the total external surface area of the human body, expressed in square meters (m2). In clinical settings, BSA is often used for medication dosing, fluid management, and physiologic assessment.
While weight alone is useful, some therapies are better scaled to body size in a way that includes both height and weight. That is where BSA formulas, including Du Bois, are commonly applied.
The Du Bois formula
The original Du Bois equation is:
This formula has been used for many decades in medicine. It remains one of the most recognized methods for estimating body surface area.
How to use this BSA calculator
- Select your preferred unit system: metric or imperial.
- Enter your height and weight values.
- Click Calculate BSA.
- Read your result in m2 (and ft2 for convenience).
Example (manual calculation)
For a person who is 175 cm and 70 kg, the Du Bois equation gives a BSA close to 1.84 m2. This is within a typical adult range, though normal values vary by sex, age, and body composition.
Common uses of BSA in healthcare
- Chemotherapy dosing: Many oncology drugs are prescribed per m2.
- Cardiology and nephrology: Some values are indexed to body size.
- Critical care: BSA may support fluid or physiologic normalization.
- Pediatrics: Pediatric dosing often uses body size scaling methods.
Important limitations
No BSA equation is perfect. Du Bois was derived from a small early dataset. In modern populations, alternative equations (like Mosteller or Haycock) may sometimes be preferred depending on context.
- BSA does not directly measure fat mass, muscle mass, or organ function.
- Extreme body sizes can reduce precision of formula-based estimates.
- Clinical decisions should always include professional judgment.
Du Bois vs. other BSA formulas
Mosteller Formula
A very common alternative is Mosteller:
BSA = √((Height(cm) × Weight(kg)) / 3600)
Mosteller is popular because it is easy to calculate and usually close to Du Bois in many adults.
Which formula should you use?
If your clinic, protocol, or textbook specifically says Du Bois, then Du Bois should be used for consistency. If no method is specified, your medical team may choose the local standard.
Frequently asked questions
Is BSA the same as BMI?
No. BMI estimates weight relative to height, while BSA estimates total body surface area.
Can I use this for children?
It can provide an estimate, but pediatric decisions should be reviewed by a qualified clinician, as age-specific considerations are important.
Is this calculator a medical diagnosis tool?
No. This tool is for educational and informational use. Medication dosing and treatment decisions should be made by licensed healthcare professionals.
Bottom line
The Du Bois BSA calculator is a practical way to estimate body surface area from height and weight. It is widely recognized, easy to apply, and especially useful when dosage or physiologic values are indexed to body size. Use it as a reliable estimate—then confirm any clinical action with your care team.