📡 Free Space Path Loss Calculator
Calculate RF signal attenuation over distance for Wi-Fi, 5G, satellite, and point-to-point links
| Frequency | 100 m | 500 m | 1 km | 10 km | 100 km |
|---|---|---|---|---|---|
| 433 MHz (LoRa) | 45.2 dB | 55.4 dB | 61.2 dB | 81.2 dB | 101.2 dB |
| 700 MHz (LTE) | 49.3 dB | 59.5 dB | 65.3 dB | 85.3 dB | 105.3 dB |
| 2.4 GHz (Wi-Fi) | 60.0 dB | 70.2 dB | 80.0 dB | 100.0 dB | 120.0 dB |
| 5 GHz (Wi-Fi) | 66.4 dB | 76.6 dB | 86.4 dB | 106.4 dB | 126.4 dB |
| 6 GHz (Wi-Fi 6E) | 68.0 dB | 78.0 dB | 88.0 dB | 108.0 dB | 128.0 dB |
| 11 GHz (P2P) | 73.3 dB | 83.5 dB | 93.3 dB | 113.3 dB | 133.3 dB |
| 28 GHz (5G) | 81.4 dB | 91.5 dB | 101.4 dB | 121.4 dB | 141.4 dB |
| 60 GHz (WiGig) | 88.0 dB | 98.0 dB | 108.0 dB | 128.0 dB | 148.0 dB |
| Antenna Type | Typical Gain | Beamwidth | Best Use Case |
|---|---|---|---|
| Dipole (half-wave) | 2.15 dBi | 360° H / 75° V | Indoor AP, general coverage |
| Rubber Duck Omni | 3–5 dBi | 360° H | Wi-Fi router, IoT devices |
| Panel/Patch | 10–18 dBi | 60–90° | Outdoor sector, P2MP |
| Yagi Directional | 10–18 dBi | 30–60° | Long-range P2P Wi-Fi |
| Parabolic Dish (30cm) | 23–25 dBi | 5–10° | Microwave P2P backhaul |
| Parabolic Dish (120cm) | 35–40 dBi | 1–3° | Satellite, long-haul P2P |
| Horn Antenna | 15–25 dBi | 10–40° | Lab reference, mmWave |
| Phased Array | 20–30 dBi | Variable | 5G NR beamforming |
| Scenario | Frequency | Distance | FSPL | Typical Link Budget |
|---|---|---|---|---|
| Home Wi-Fi (2.4 GHz) | 2.4 GHz | 15 m | 51.6 dB | ~100 dB margin |
| Home Wi-Fi (5 GHz) | 5 GHz | 10 m | 66.4 dB | ~90 dB margin |
| Outdoor Wi-Fi AP | 5 GHz | 100 m | 86.4 dB | ~110 dB budget |
| P2P Building Link | 5.8 GHz | 500 m | 101.7 dB | ~130 dB budget |
| LTE Macro Cell | 850 MHz | 3 km | 101.6 dB | ~150 dB budget |
| 5G mmWave Small Cell | 28 GHz | 200 m | 107.4 dB | ~130 dB budget |
| Microwave Backhaul | 11 GHz | 10 km | 133.3 dB | ~160 dB budget |
| LEO Satellite | 12 GHz | 550 km | 187.3 dB | ~200 dB budget |
| Standard | Frequency | Max TX Power | Typical Range |
|---|---|---|---|
| IEEE 802.11b/g/n | 2.4 GHz | 100 mW (20 dBm) | ~50–100 m indoor |
| IEEE 802.11a/n/ac | 5 GHz | 200 mW (23 dBm) | ~30–50 m indoor |
| IEEE 802.11ax (Wi-Fi 6) | 2.4 / 5 GHz | 200 mW (23 dBm) | ~30–100 m indoor |
| IEEE 802.11ay (Wi-Fi 6E) | 60 GHz | 10 mW (10 dBm) | ~10 m NLOS, 100m LOS |
| 3GPP LTE (FDD) | 700 MHz–2.6 GHz | 23–43 dBm | 1–10 km cell |
| 3GPP 5G NR Sub-6 | 600 MHz–6 GHz | 23–43 dBm | 500 m–5 km |
| 3GPP 5G NR mmWave | 24–100 GHz | 23–33 dBm | 50–300 m |
| ITU-R P.525 FSPL | All | N/A | Formula standard |
Free space path loss, or FSPL for short, describes simply what happens when a radio signal dies as it travels through open air or vacuum. Think about it like this: radio waves lose energy in bigger amounts the farther they go from the source. The more far they go the more they die.
It is that simple.
What Is Free Space Path Loss (FSPL)?
FSPL counts only in ideal cases. No blocks on the way, no bouncing of signals from walls, no noise. It shows the expected loss that one would see in perfect vacuum, that imaginary setting where nothing gets in the way.
Here is what we understand by free space, and FSPL guesses how far radio waves lose power as they travel.
The reason that signals die over distance comes down to something called the reverse square law. When a signal spreads outside, it covers an always bigger surface. This spreading causes the power to spread over a wider area, so the signal strength drops.
Specifically, the loss gorws with the square of the distance between sending and receiving antennas. If you double the distance, you get a heavy drop in signal strength.
Frequency has big influence too. Signals at higher frequencies. For instance 5 GHz; suffer bigger loss than those at low frequencies.
A signal at 5 GHz has more path loss than one at the 2.4 GHz band. Interesting though is that the formulas show that path loss simply grows with the frequency. That does not show the whole picture.
Antenna gain depends on frequency, so when one considers the frequency-based part of the FSPL formula, one ends with something called spreading loss.
The practical formula is this: FSPL equals 32.44 plus 20 logarithm of the distance in kilometers, plus 20 logarithm of the frequency in MHz. The result comes in decibels. Here are the main points, calculations of FSPL do not consider antenna gains of the sender ore of the receiver.
Only the loss on the way itself is measured. Said that, FSPL helps well to guess signal strength at a given distance.
Knowing FSPL is useful for guessing Wi-Fi coverage. It forms the most basic model about how radio signals spread. The problem is that real life almost never follows this ideal.
Ground factors and harmful noise happen near the antenna. Indoor spaces cause multipath problems that quickly get complex. In such hard cases, some models use reverse sixth order for loss instead of the usual reverse square guess.
Mobile nets must deal also with delay spread and Doppler shift, whichfurther complicates things.
FSPL works only in conditions close to vacuum. For real communications, one must consider hills, trees, rain and buildings (all of them eat from your signal). The model of path loss over distance works better for capturing real-world settings compared to basic FSPL.
