Calculate effective projected area from drag coefficient and frontal area, estimate steady-flow wind force from EPA, speed, density, or flat-shape dimensions. These simplified models do not replace code-based structural wind design; openness reductions are geometric approximations.

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Presets are illustrative. Cd must match the reference area and flow conditions.

Result unit

Effective Projected Area Formula

The following two example problems outline the steps and information needed to calculate the Effective Projected Area.

EPA = D ร— FPA
  • Where EPA is the Effective Projected Area
  • D is the drag coefficient 
  • FPA is the frontal projected area 

To calculate the effective projected area, multiply the drag coefficient by the frontal projected area.

How to Calculate Effective Projected Area?

The following example problems outline how to calculate Effective Projected Area.

Example Problem #1:

  1. First, determine the drag coefficient.
    • The drag coefficient is given as .75.
  2. Next, determine the frontal projected area.
    • The frontal projected area is provided as 300 ftยฒ.
  3. Finally, calculate the Effective Projected Area using the equation above: 

EPA = D * FPA

The values provided above are inserted into the equation below and computed.

EPA = .75 * 300 ftยฒ = 225 ftยฒ

Example Problem #2: 

For this problem, the variables required are provided below:

drag coefficient = .50

frontal projected area = 100 ftยฒ

Test your knowledge using the equation and check your answer with the calculator.

EPA = D * FPA = ?