The dBi Range Calculator helps determine the effective range of an antenna based on its gain (dBi), frequency, and transmitted power. This tool is crucial in wireless communication, radio frequency (RF) engineering, and antenna design, where signal coverage is a key factor.
This calculator is useful in:
- Wi-Fi network planning – Determining signal reach for routers
- Satellite and radio communications – Evaluating signal loss over distance
- Drone and UAV telemetry – Ensuring stable long-range communication
- RF and microwave engineering – Optimizing antenna design for better coverage
By calculating free-space path loss (FSPL), the tool helps users optimize antenna placement, maximize signal coverage, and improve communication efficiency.
Formula for Dbi Range Calculator
The range of an antenna is influenced by:
- Antenna Gain (dBi) – A measure of how well an antenna focuses energy
- Transmission Frequency (Hz) – Higher frequencies experience more loss
- Distance (m) – The greater the distance, the weaker the received signal
The Free-Space Path Loss (FSPL) Formula is used to estimate signal loss over distance:
FSPL Formula
FSPL (dB) = 20 × log10(Distance) + 20 × log10(Frequency) + 20 × log10(4π / c)
Where:
- Distance (m) = The range to calculate
- Frequency (Hz) = Transmission frequency
- c = 3 × 10⁸ m/s = Speed of light
- 4π = Spherical wavefront expansion
Rearrange for Distance
To calculate maximum transmission distance, we use:
Distance (m) = 10^((dBi - FSPL) / 20) × Reference Distance
This formula helps estimate how far a signal can travel before becoming too weak for reliable communication.
Reference Table – Antenna Range Estimations
For ease of use, here’s a reference table showing estimated transmission distances for different antenna gains at 2.4 GHz (Wi-Fi frequency):
| Antenna Gain (dBi) | Distance (Meters) | Distance (Kilometers) |
|---|---|---|
| 0 dBi (Omni) | ~100 m | 0.1 km |
| 3 dBi (Dipole) | ~250 m | 0.25 km |
| 6 dBi | ~500 m | 0.5 km |
| 9 dBi | ~1,000 m | 1.0 km |
| 12 dBi | ~2,000 m | 2.0 km |
| 15 dBi | ~4,000 m | 4.0 km |
| 20 dBi | ~10,000 m | 10.0 km |
Note: These values assume ideal free-space conditions with no obstacles. Actual range may vary due to interference, obstructions, and atmospheric conditions.
Example of Dbi Range Calculator
1. Calculate Range for a 9 dBi Antenna at 2.4 GHz
Using the FSPL formula:
FSPL = 20 × log10(Distance) + 20 × log10(2.4 × 10⁹) + 20 × log10(4π / 3 × 10⁸)
Rearrange for Distance:
Distance = 10^((9 - FSPL) / 20) × Reference Distance
Approximating, we get 1 km (1,000 meters) for a 9 dBi antenna at 2.4 GHz in free-space conditions.
2. Calculate Range for a 15 dBi Antenna at 5 GHz
For a 15 dBi antenna operating at 5 GHz, the increased frequency results in higher path loss, reducing range. Using the same formula, the estimated range is around 2 km.
Most Common FAQs
dBi (decibels relative to an isotropic radiator) measures how much an antenna amplifies signals in a specific direction compared to a perfect spherical radiator. Higher dBi means greater directional focus and longer range.
Higher frequencies experience greater path loss due to increased atmospheric absorption and material penetration losses, making long-distance communication harder.