# Free-Space Path Loss (wavelength)

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FSPL =
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DavidC.Free-Space Path Loss (wavelength)
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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 wavelength (λ) of the signal.

INSTRUCTIONS: Choose the preferred units and enter the following:

• (d) This is the distance between receivers.
• (λ) This is the wavelength 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.

#### General Information

The formula for the Free-Space Path Loss based on wavelength used in this calculator is:

FSPL =  ((4 pi * d*f)/λ)^2

where:

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

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.