WiFi Free Space Loss Calculator


This wireless calculator can be used in the installation of radio and wireless systems. WiFi signal strength reduces with distance of the transmitter from the receiver. To understand the reasons for the free space path loss, it is possible to imagine a signal spreading out from a transmitter. It will move away from the source spreading out in the form of a sphere. As it does so, the surface area of the sphere increases. As this will follow the law of the conservation of energy, matter cannot be created or destroyed, as the surface area of the sphere increases, so the intensity of the signal must decrease.

Enter Frequency (Ghz):

EIRP: (dBm) Distance: (m) Signal Level (dBm):
Loss (dB):

To get an estimate what a signal level might be over a particular distance, simply select the WIFI channel you are interested in. Enter the EIRP, effective radiated power of your wifi device transmitter. Enter the distance involved. Then hit the Calculate button.

This is a theoretical signal loss in free space, once you have obstructions, the signal strength will be different. The actual signal level received by the wifi receiver  will depend on the gain (or loss) of its antenna).

Although the free space loss seems to indicate that the signal level loss is frequency dependent, the attenuation provided by the distance travelled in space is not dependent upon the frequency. This is constant.

The reason for the frequency dependence is that the calculation contains two effects:

  1. The first results from the spreading out of the energy as the sphere over which the energy is spread increases in area. This is described by the inverse square law.

  2. The second effect results from the antenna aperture change. This affects the way in which any antenna can pick up signals and this term is frequency dependent.

As one constituent of the path loss calculation is frequency dependent, this means that there is a frequency dependency within the complete calculation.

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Energy cannot be created or destroyed; it can only be changed from one form to another. This is a fact to consider if you believe in the evolution of the universe.

If energy can't be created where did it come from in the first place. Investigate why energy can't be destroyed also. Matter cannot be created or destroyed

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