Friis Path Loss Calculator: Accurate Free Space Loss (FSPL) for RF Systems

Calculate Friis Free Space Path Loss (FSPL)

Please enter a valid positive distance.
Please enter a valid positive frequency.

Calculation Results

Friis Free Space Path Loss (FSPL):

Use our Friis Path Loss Calculator to accurately estimate signal attenuation in free space. This essential tool helps RF engineers, network planners, and hobbyists design robust wireless communication systems by predicting signal strength over distance. Easily analyze the impact of distance and frequency on RF signal propagation.

Formula:

The Friis Path Loss formula is fundamental for calculating the theoretical signal attenuation between two isotropic antennas in free space, assuming no obstacles or reflections. The formula used in this calculator is:

LP (dB) = 32.45 + 20 log10(d) + 20 log10(f)

Where:

  • LP = Free Space Path Loss in decibels (dB)
  • d = Distance between the transmitting and receiving antennas in kilometers (km)
  • f = Frequency of the radio signal in Megahertz (MHz)

This simplified version of the Friis formula is commonly used when distance is in kilometers and frequency is in Megahertz.

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