The Field Strength To Power Density Calculator helps engineers, researchers, and safety officers convert an electric field measurement into a power density value. This is important for understanding how much electromagnetic energy is present in an area, which affects wireless signals, antenna performance, and safety compliance with exposure limits. By using this tool, professionals can ensure that power levels stay within safe or regulated ranges. This calculator belongs to the Electromagnetic Field and RF Safety Calculator category and is widely used in telecommunications, broadcasting, and health physics.
formula of Field Strength To Power Density Calculator
Power Density (S) = (E²) / (Z₀)
Where:
S is the power density (in watts per square meter, W/m²)
E is the electric field strength (in volts per meter, V/m)
Z₀ is the characteristic impedance of free space, about 377 ohms
Full formula:
S = E² / 377
If both electric (E) and magnetic (H) fields are known, an alternate form is:
S = E × H
Where:
H is the magnetic field strength (in amperes per meter, A/m)
For free space, H can be found using: H = E / 377
Both forms give the same result for free space.
Common Field Strength and Power Density Reference Table
This table shows some typical electric field values and the matching power densities for quick checks.
| Electric Field (V/m) | Power Density (W/m²) |
|---|---|
| 1 | 0.00265 |
| 10 | 0.265 |
| 20 | 1.06 |
| 50 | 6.63 |
| 100 | 26.5 |
| 200 | 106.1 |
This helps you understand what power levels are linked to certain field strengths.
Example of Field Strength To Power Density Calculator
Let’s check an example step by step.
Suppose the electric field strength measured near a broadcast tower is 50 V/m.
- Use the formula:
S = E² / 377
S = (50)² / 377
S = 2,500 / 377
S ≈ 6.63 W/m²
This means the power density at that location is about 6.63 watts per square meter.
Most Common FAQs
Power density shows how much electromagnetic energy passes through a surface. It is an important value for checking wireless system performance and making sure exposure levels are safe for people working near antennas or towers.
Yes, 377 ohms is the approximate impedance of free space. In other materials or near conductors, the value can change. For standard air or free space, always use 377 ohms.
Always use volts per meter (V/m) for electric field strength and get power density in watts per square meter (W/m²). For magnetic field strength, use amperes per meter (A/m).