What Is a WiFi Free Space Path Loss Distance Calculator?
Free Space Path Loss (FSPL) describes how much a radio signal weakens purely from spreading out over distance, with no walls, weather or interference involved. By comparing your transmit power to the signal strength your device actually receives, this calculator estimates the loss and works backward through the FSPL formula to estimate the line-of-sight distance to the access point.
This is the foundational equation from Friis transmission theory that RF engineers use to plan wireless links, from WiFi networks to satellite communications.
How to Read Your Results
Estimated Distance
The approximate line-of-sight distance implied by your signal strength readings, shown in the most readable unit (meters or kilometers).
Path Loss
The difference between your transmit power and received signal strength, in decibels — this is the total signal attenuation between transmitter and receiver.
Frequency Used
Higher frequencies (like 5GHz or 6GHz WiFi) attenuate faster with distance than lower frequencies (like 2.4GHz), even at the same transmit power.
Real-World Example
Your router transmits at 20 dBm on the 2.4GHz band, and your laptop reports a received signal strength of −65 dBm.
| Field | Value |
|---|---|
| Transmit power | 20 dBm |
| Received signal strength | −65 dBm |
| Path loss | 85 dB |
| Estimated distance | ≈176.9 m |
An 85 dB path loss at 2.4GHz corresponds to roughly 177 meters of open-air, line-of-sight distance — but through several interior walls, the real distance to reach −65 dBm would be much shorter since walls add extra loss beyond free space.
Tips for Using This Calculator
- Free space assumes no obstructions. Indoors, actual coverage distance is always shorter than the free-space estimate for the same signal strength.
- Higher frequency bands (5GHz, 6GHz) have shorter effective range than 2.4GHz at the same power, but often offer faster speeds up close.
- Received signal strength around −50 to −60 dBm is excellent; below about −80 dBm is typically too weak for a reliable connection.
- Antenna gain isn't included in this simplified calculation — directional antennas can extend real range well beyond this estimate.
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Last updated: August 2026 · Reviewed by: Simple Calculator Tools Editorial Team