What is body surface area?
Body surface area (BSA) is the estimated size of the outer surface of the body in square metres (m²). Because it is impractical to measure directly, it is calculated from weight and height. Average adult values are about 1.6 m² in women and 1.9 m² in men.
Which formulas are used?
- Mosteller: √(height (cm) × weight (kg) / 3600). The most widely used in clinical practice because it is simple.
- DuBois and DuBois: 0.007184 × weight^0.425 × height^0.725. Described in 1916 and long used as the reference.
- Haycock: 0.024265 × weight^0.5378 × height^0.3964. Validated in children and infants as well.
In adults of average build the formulas give similar results; the differences grow in marked obesity, very low weight or limb loss.
Where is BSA used?
- Dosing of some drugs, especially chemotherapy
- Indexing cardiac measurements such as the cardiac index
- Standardising kidney function (GFR) to 1.73 m²
- Some drug and fluid calculations in children
With this tool you can quickly find your body surface area and better understand what this value means when it is used in your care. The result is for information only; treatment and dosing decisions are made by the physician after assessing your overall health.
Frequently Asked Questions
Which formula is most accurate?
No single formula has been shown to be best in every situation. Mosteller is used most often because it is simple; DuBois has long been the reference. The treating team decides which formula to use.
What is a normal body surface area?
There is no single normal value; it depends on weight and height. Average adult values are about 1.6 m² in women and 1.9 m² in men.
Can I work out my medicine dose with this calculator?
No. Drug doses are set only by the treating physician, taking weight, kidney and liver function, the treatment protocol and other clinical information into account.