Estimate body surface area (BSA) quickly and accurately using height and weight with trusted clinical formulas like Mosteller, Du Bois, and Haycock.
What is Body Surface Area (BSA)?
Body surface area is the total external surface area of the human body, typically expressed in square meters (m²). BSA is used across clinical practice and research because it often correlates better than weight alone with physiological variables such as cardiac output, blood volume, and metabolic rate. It also underpins important dosing and assessment decisions in oncology, nephrology, and critical care.
Why use a Body Surface Area calculator?
- Medication dosing: Many chemotherapy regimens and other medications are prescribed per m² of BSA.
- Renal and hepatic adjustments: BSA may be used to normalize lab values and dosing thresholds.
- Fluid and nutritional planning: Estimations can support tailored fluid, caloric, or protein targets.
- Research and indexing: BSA indexes physiological measures, enabling fair comparisons across body sizes.
Common BSA formulas supported
Mosteller
The Mosteller formula is popular for its simplicity and clinical reliability. It calculates BSA as the square root of the product of height (cm) and weight (kg) divided by 3600. This balance of practicality and accuracy has made it a frequent default in care settings.
Du Bois
One of the earliest BSA equations, Du Bois uses an allometric approach with exponents applied to height and weight. It remains widely cited in academic literature and is considered a classic reference standard.
Haycock
The Haycock formula refines allometric exponents to improve fit across a range of body sizes, including pediatric populations. Many clinicians consult it when they want an alternative to Mosteller or Du Bois.
How to use the calculator
- Enter weight and choose kilograms or pounds.
- Enter height and choose centimeters or inches.
- Select your preferred formula: Mosteller (default), Du Bois, or Haycock.
- Pick your desired decimal precision.
- Press Calculate to see BSA in square meters (m²).
BSA vs. BMI: What’s the difference?
Body mass index (BMI) describes weight relative to height and is used to classify underweight, normal weight, overweight, and obesity categories. BSA, however, estimates overall body surface area. While BMI is useful for population screening, BSA is better suited for clinical tasks like drug dosing and indexing organ function. They serve different purposes and can be complementary when assessing an individual’s health and treatment plan.
Accuracy tips
- Measure height without shoes and stand upright against a wall.
- Use a calibrated scale for weight and measure at a consistent time of day.
- Choose the formula preferred by your clinical guidelines or institution.
- Remember that all formulas provide estimates; clinical judgment remains essential.
Clinical disclaimer
This Body surface area calculator is an educational tool and does not provide medical advice. Always confirm dosing and treatment decisions using your organization’s protocols, drug monographs, and professional guidance.