dBi stands for deciBel isotropic [1]. It is the gain of an antenna relative to that of a theoretical isotropic antenna [2].

An Isotropic antenna radiates energy equally in all directions. By contrast a directional antenna focuses energy in a particular direction. The higher the dBi value, the more focused the antenna beam.

Use this Calculator to find the Antenna dBi Gain using:

- Antenna Factor (dB/m)
- Frequency of operation (Hz/kHz/MHz/GHz)

**dBi Formula**

**Gain (dBi) = 20*Log _{10}(9.73/[λ***

**(10)**

^{AF/20}])Where

**λ**= Wavelength =**c/f**, where**c**is the speed of light and**f**is the frequency**AF**= Antenna Factor

Note that **dBi** represents a ratio and not an absolute quantity.

**Related Calculators**

Use our

- dBi to dBm converter to calculate the maximum transmit power for a specified EIRP (Effective Isotropic Radiated Power)
- dBm to dBi converter to determine the maximum antenna gain such that the EIRP doesn’t exceed the FCC specified limit.

**Application**

The higher the dBi, the more focused the energy and the higher the antenna gain.

Helium hotspot owners use high gain antennas to focus in a direction with larger numbers of witnesses. The highest gain we’ve seen in practical use is 8 dBi.

Many TV antennas are of the directional Yagi-Uda type (shown in the picture below) and can be pointed in the direction of the transmitting tower for better signal reception.

**References**

[1] DeciBel Antenna Measurements on Wikipedia

[2] Isotropic Radiator on Wikipedia