Free-Space Path Loss Calculator
Estimate ideal free-space RF path loss from frequency and distance.
Free-Space Path Loss Calculator
How to use the Free-Space Path Loss Calculator
Enter the signal frequency and unobstructed path distance. The calculator returns the theoretical free-space loss in dB.
How it works
Free-space path loss estimates the spreading loss between ideal antennas with a clear line of sight. It is calculated from frequency and distance and is expressed in decibels.
Example: A 2.4 GHz signal travelling 1 km has a free-space path loss of about 100.05 dB before antenna gains, cable losses or environmental effects are considered.
What to keep in mind
The model excludes buildings, terrain, foliage, weather, Fresnel-zone obstruction, antenna polarisation and multipath. Real links should include appropriate additional losses and fade margin.
Frequently asked questions
Why does loss increase with frequency?
For the same distance and ideal antenna gains, free-space spreading loss increases as wavelength becomes shorter.
Does this predict indoor coverage?
Not reliably. Walls, reflections and obstructions dominate many indoor paths.
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