Calculate effective area, incident wave intensity, or power by choosing a solve mode and entering its two required values and converting between W/m², m², W, kW, HP, ft², yd².
Effective Area Formula
The effective area relationship connects incident wave intensity, effective area, and power. The calculator uses watts and square meters as base units, then converts the result back to the unit you selected.
- P = power, usually in watts (W)
- I = incident wave intensity, usually in watts per square meter (W/m²)
- A = effective area, usually in square meters (m²)
The calculator has three functions:
- Calculate power: enter incident wave intensity and effective area. The calculator uses P = I × A.
- Calculate effective area: enter power and incident wave intensity. The calculator uses A = P ÷ I.
- Calculate incident wave intensity: enter power and effective area. The calculator uses I = P ÷ A.
If you enter values in W/ft², ft², yd², kW, or horsepower, the calculator converts them to base units first. It uses W/m² for intensity, m² for area, and W for power during the calculation.
Unit Conversions Used for Effective Area Calculations
These are the main conversion factors used before applying the formula.
| Quantity | Unit | Base-unit conversion |
|---|---|---|
| Incident wave intensity | W/m² | 1 W/m² |
| Incident wave intensity | W/ft² | 1 W/ft² ≈ 10.763910417 W/m² |
| Effective area | ft² | 1 ft² = 0.09290304 m² |
| Effective area | yd² | 1 yd² = 0.83612736 m² |
| Power | kW | 1 kW = 1000 W |
| Power | HP | 1 mechanical HP ≈ 745.699872 W |
Common Rearrangements of the Effective Area Equation
| Missing value | Use this formula | Required inputs |
|---|---|---|
| Power | P = I × A | Incident wave intensity and effective area |
| Effective area | A = P ÷ I | Power and incident wave intensity |
| Incident wave intensity | I = P ÷ A | Power and effective area |
Example Calculations
Example 1: Calculate power
You have an incident wave intensity of 250 W/m² and an effective area of 2.4 m².
The power is 600 W, or 0.6 kW.
Example 2: Calculate effective area
You have a power value of 1.5 kW and an incident wave intensity of 75 W/m².
First convert power to watts:
Then calculate area:
The effective area is 20 m², which is about 215.28 ft².
FAQ
What is effective area?
Effective area is the area that would capture or receive a given amount of power from an incident wave at a given intensity. It is not always the same as the physical surface area. In many wave and antenna problems, effective area represents how much of the incoming wave is effectively used or received.
Why do I need to enter exactly two values?
The equation has three variables: power, incident wave intensity, and effective area. If you know any two of them, the third can be calculated. If you enter only one value, there is not enough information. Choose the value to solve for; only its two required input fields are shown.
Can area or intensity be zero?
Area and intensity cannot be zero when they are used as divisors. For example, calculating effective area requires A = P ÷ I, so intensity cannot be zero. Calculating intensity requires I = P ÷ A, so area cannot be zero.
