Free-Space Path Loss (using frequency)

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Equation / Last modified by KurtHeckman on 2018/08/15 19:10
DavidC.Free-Space Path Loss (using frequency)

The Free-space Path Loss (FSPL) calculator computes the loss of signal strength on a line-of-sight path which has no obstacles or other disturbances based on the distance (d) and the frequency (f) of the signal.  

INSTRUCTIONS: Choose the preferred units and enter the following:

  • (d) This is the distance between receivers.
  • (f) This is the frequency of the signal.

Free-Space Path Loss: The calculator returns the loss in dB.  However, this can be automatically converted to a real or percent via the pull-down menu.

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General Information

The formula for the Free-Space Path Loss using frequency is:

FSPL = ` ((4 pi * d*f)/c)^2`


  • FSPL is the Free-space path loss
  • d is the distance between receivers.
  • f is the frequency of the signal.

This equation uses the frequency and the constant for speed of light to calculate the FSPL.

This equation is only accurate at a distance from the transmitter where spherical spreading can be assumed.  This equation is not accurate for short distances.