Free Space Path Loss
How much a Wi-Fi signal weakens between two antennas in open space, and why. Move the receiver away and watch the inverse square law at work.
How to use this tool controls and what to look for
Choose a frequency and distance, and watch the received power drop as the receiver moves further away.
Controls to change
- Frequency: pick 2.4, 5 or 6 GHz, or enter a Custom frequency in MHz.
- Distance: drag the slider, or use ×2 and ÷2 to double or halve it.
- Transmit power: set the transmitter power in dBm.
- Tx antenna gain: add antenna gain at either end (Rx antenna gain for the receiver).
- dB scale: switch the chart between the dB scale and Linear (watts).
- 1× distance: in The inverse square law, switch between 1×, 2× and 4× the distance and see the same energy spread over a larger area.
What to look for
- Every doubling of distance costs 6 dB, whatever the starting point.
- At the same distance, 5 and 6 GHz lose about 6–8 dB more than 2.4 GHz with the same antennas.
- In watts the loss is a steep curve. On the dB scale it becomes a straight line against log distance.
About this tool
Free space path loss is how much a signal weakens between two antennas with nothing in the way. This tool shows the received power as you move the receiver away, the inverse square law behind it, and why higher frequencies lose more between the same antennas. Enter the transmit power, antenna gains, frequency and distance to see the signal that arrives.
What you'll learn
- The formula: FSPL (dB) = 20 log10(distance in km) + 20 log10(frequency in MHz) + 32.44
- Why every doubling of distance costs 6 dB
- Why 5 GHz and 6 GHz lose about 6–8 dB more than 2.4 GHz with the same antennas
- How to turn path loss into received power
Common questions
How much signal does Wi-Fi lose over distance?
About 40 dB in the first metre at 2.4 GHz and about 47 dB at 5 GHz, then another 6 dB every time the distance doubles.
Why does 5 GHz have less range than 2.4 GHz?
With the same antennas, free space loss is about 6 dB higher at 5 GHz, and walls and people also absorb more at higher frequencies.
Is free space path loss realistic indoors?
It is the best case. Walls, furniture and people add more loss, so treat it as a starting point for a link budget, not a coverage prediction.
Free for private and educational use. This interactive model is a simplified teaching aid and may contain mistakes. It is provided as is, without warranty. Use it to understand the concepts, not as a substitute for a site survey, vendor documentation or professional design advice.