Free Space Path Loss Calculator

Calculate the signal attenuation in free space between a transmitter and receiver.

What is path loss?

Like shouting across a field — the farther away someone is, the quieter it sounds. RF signals weaken with distance in the same way. Higher frequencies also fade faster than lower ones.

Why does this matter?

Cell tower engineers use path loss calculations to determine how many towers are needed to cover a city. Too few towers and the signal becomes too weak; too many wastes money. This calculator gives the baseline "best case" loss in open air.

Signal Parameters
Enter frequency and distance for path loss calculation.

Higher frequencies lose more power over distance. WiFi at 5 GHz has more path loss than at 2.4 GHz, which is why 5 GHz has shorter range.

km

The straight-line distance between transmitter and receiver. Obstacles like buildings or hills add extra loss beyond this free-space baseline.

0.1 km1.0 km1000 km
Path Loss Result
Free Space Path Loss100.0dBModerate
Frequency2.400 GHz
Distance (km)1.000 km
Distance (miles)0.621 mi
FSPL at 1 km (same freq)100.0 dB
Additional loss (×10 distance)+20 dB

Free-space path loss assumes an unobstructed line-of-sight path with no reflections, absorption, or diffraction. Real-world links have additional losses from terrain, atmosphere, and rain fade.