# dBi Calculator

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

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:

## dBi Formula

Gain (dBi) = 20*Log10(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.