Calculator Inputs
Large screens show three columns, medium screens show two, and mobile shows one.
Example Data Table
Example values below illustrate how changing frequency, gain, and distance affects average power density and comparison margins.
| Scenario | Frequency | TX Power | Gain | Distance | Type | Avg Power Density | Limit | Result |
|---|---|---|---|---|---|---|---|---|
| Cellular rooftop sector | 900 MHz | 40 W | 15 dBi | 10 m | General public | ~0.711 W/m² | 6.000 W/m² | Within limit |
| Industrial WLAN bridge | 2450 MHz | 20 W | 18 dBi | 5 m | Occupational | ~3.190 W/m² | 50.000 W/m² | Within limit |
| Small 5G point link | 3500 MHz | 5 W | 8 dBi | 2 m | General public | ~0.396 W/m² | 10.000 W/m² | Within limit |
Formula Used
Power at Antenna = Transmitter Power ÷ 10^(Cable Loss dB ÷ 10)
Gain Linear = 10^(Gain dBi ÷ 10)
Nominal EIRP = Power at Antenna × Gain Linear
Adjusted EIRP = Nominal EIRP × Duty Cycle × Reflection Factor × Environment Factor
Power Density = EIRP ÷ (4 × π × Distance²)
E = √(377 × S) and H = E ÷ 377
Wavelength = 300 ÷ Frequency in MHz
Reactive Near-Field Start ≈ 0.62 × √(D³ ÷ λ)
Far-Field Boundary ≈ 2 × D² ÷ λ
Safe Distance = √(Adjusted EIRP ÷ (4 × π × Selected Limit))
This calculator compares average power density against common far-field style MPE thresholds. It is an engineering estimator, not a substitute for a site survey or formal compliance study.
How to Use This Calculator
- Enter the operating frequency in MHz.
- Enter transmitter output power before feeder loss.
- Add antenna gain in dBi and cable loss in dB.
- Enter the separation distance between the antenna and the evaluation point.
- Set duty cycle to reflect average transmitter activity.
- Increase reflection and environment factors only when you want a conservative estimate.
- Enter the largest antenna dimension to estimate region classification.
- Set body area and exposure duration to estimate incident power and energy.
- Select general public or occupational comparison mode.
- Press the calculate button to show results above the form and review the graph, limits, and safe distances.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates far-field style RF exposure using transmitter power, antenna gain, losses, distance, duty cycle, and optional conservative multipliers. It also reports EIRP, field strength, region classification, safe distance, incident body power, and comparison against selected thresholds.
2) Is this suitable for compliance certification?
It is useful for engineering screening and planning, but it is not a certification tool. Formal compliance may require local regulations, measured data, pattern files, spatial averaging, near-field analysis, and documentation prepared by qualified specialists.
3) Why does distance reduce exposure so quickly?
In far-field conditions, power spreads over a larger spherical area as distance increases. That causes power density to fall with the square of distance. Doubling the distance reduces power density to one quarter.
4) What is the difference between nominal and adjusted EIRP?
Nominal EIRP uses transmitter power, feeder loss, and antenna gain only. Adjusted EIRP also includes duty cycle and optional conservative factors, making it more useful for average exposure estimates in practical environments.
5) Why does the calculator show near-field warnings?
The inverse-square method works best in far-field conditions. Close to large antennas, actual field behavior becomes more complex. Near-field estimates can differ substantially from measurements, so the calculator warns when distance is inside those boundaries.
6) What does the body area input do?
Body area is used to estimate the incident power and energy intercepting a selected exposed area. It does not replace SAR calculations or tissue models, but it helps with screening-level energy exposure interpretation.
7) Should I increase reflection and environment factors?
Use higher factors only when you need a more conservative estimate, such as reflective rooftops, metal-rich spaces, or uncertain site conditions. For clean line-of-sight free-space screening, values near 1.00 are usually appropriate.
8) Which comparison type should I choose?
Choose general public for uncontrolled areas accessible to the public. Choose occupational for controlled work areas where trained personnel follow safety procedures and access is managed during operation or maintenance.