Free-Space Path Loss Calculator
How much signal strength does a wireless link lose over distance?
Your numbers
Your results
Free-Space Path Loss Calculator by TheCalcTools
How the Free-Space Path Loss Calculator works
Enter the distance in kilometres and the frequency in megahertz.
Path loss increases by 6 dB each time distance or frequency doubles.
The result assumes a clear line of sight with no obstacles, reflections or fading.
The formula
Worked example
Using the default values shown in the calculator:
| Distance (km) | 10 |
|---|---|
| Frequency (MHz) | 2400 |
- 20 log₁₀(10) = 20 dB.
- 20 log₁₀(2,400) = 67.60 dB.
- Adding 32.44 gives 120.04 dB.
Result:
| Path loss (dB) | 120.04 |
|---|---|
| Wavelength (m) | 0.1249 |
Frequently asked questions
Is free-space loss realistic?
It is the ideal minimum. Real links also lose power to trees, walls, rain and multipath, so add a fade margin.
Why does a higher frequency lose more?
For the same antenna gains, a shorter wavelength means a smaller effective antenna area, so more power is lost over the same distance.
Sources and further reading
Related calculators
More in Cloud & Networking · All calculators
This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.