Physics

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Free-Space Path Loss Calculator.

Calculate Friis free-space path loss from frequency and distance.

On-device calculationNo signup
01

Set your values

Results update as you type.

Wavelength: 0.124914 m

Wavelength

0.000000m
Path loss: 80.052008 dB

Path loss

0.000000dB

Results update automatically as you type.

Use Cases

Link Budget Planning

Estimate the signal attenuation between a transmitter and receiver in free space to help design wireless communication links.

Example: Calculate path loss for a 2.4 GHz Wi-Fi signal over 100 meters.

Antenna Range Estimation

Determine how much signal loss to expect over a given distance for a specific frequency, aiding in antenna placement and coverage analysis.

Example: Estimate loss for a 5.8 GHz link over 1 km.

Frequently Asked Questions

What is free-space path loss?
Free-space path loss (FSPL) is the attenuation of a radio signal as it travels through free space, assuming no obstacles or reflections. It is calculated using the Friis transmission equation and depends on frequency and distance.
How is free-space path loss calculated?
The calculator uses the Friis formula: FSPL (dB) = 20*log10(distance) + 20*log10(frequency) + 20*log10(4π/c), where c is the speed of light. You input frequency in Hz and distance in meters, and it outputs the path loss in dB.
What units does the calculator use?
The calculator requires frequency in Hertz (Hz) and distance in meters (m). The result is given in decibels (dB). Ensure you convert your values to these units before entering them.

Tips & Common Mistakes

Tips

  • Ensure frequency is in Hz (e.g., 2.4 GHz = 2,400,000,000 Hz) and distance in meters (e.g., 1 km = 1000 m).
  • This calculator assumes ideal free-space conditions; real-world environments with obstacles will have additional losses.
  • Use the result as a reference for relative comparisons, not as an absolute prediction of signal strength.
  • For quick estimates, remember that doubling the distance adds about 6 dB to the path loss.

Common Mistakes to Avoid

  • Forgetting to convert units: entering GHz as Hz or km as m will produce incorrect results.
  • Using the calculator for non-free-space scenarios (e.g., indoor or urban) without accounting for extra losses.
  • Misinterpreting the result as absolute signal power; it is only the loss between isotropic antennas.

Last updated: August 13, 2026