Using the Body Surface Area Calculator
Use centimeters for height and kilograms for weight. The formula takes the square root of their product divided by 3,600. Because of that square root, doubling one input does not double the result. The calculator does not collect any treatment or medication information.
Worked example
Use the example inputs below to reproduce this result. These are the form's starting values, not recommended targets. Changing your inputs updates your result above; this worked example stays fixed for comparison. Results are rounded for display.
Example inputs
- Weight (kg)
- 70
- Height (cm)
- 175
Example result
- Body surface area (m²)
- 1.844662
Method and assumptions
Mosteller: √(height in cm × weight in kg / 3600). Do not use this estimate alone to choose medication doses.
Keep the equation with the result
A clinical estimate is easier to interpret when its equation, units and input values are recorded together. Different formulas can answer related questions without producing identical values. The decimal output does not remove uncertainty in the measurements or model. A qualified clinician can interpret the result in the context of the other information this form does not collect.
Common question
Why might another BSA calculator give a slightly different answer?
There are several body-surface-area equations. They use different coefficients or relationships between height and weight, so the same measurements can produce different estimates. When a specific method is required, use the equation specified by the relevant professional or protocol.
Guide updated .