dBd to dBi Calculator

This handy tool converts antenna gain from deciBel relative to a dipole (dBd) to deciBel relative to an isotropic antenna (dBi).


Enter the dBd value and the tool will compute the dBi gain value.



🔄 dBi to dBd


Gain (dBi) = Gain (dBd) + 2.15


The terms dBi and dBd are used to describe the gain of an antenna compared to a reference. They are both units of measure to express the gain, but they use different references.

dBi – what does it mean?

dBi stands for decibels relative to an isotropic radiator. An isotropic radiator is a theoretical point source of electromagnetic waves that radiates the same intensity of radiation in all directions. It has no physical form but serves as a useful comparison standard.

When the gain of an antenna is given in dBi, it means the gain is compared to the isotropic radiator. A higher dBi value indicates a stronger antenna that can send or receive signals more effectively over distance.

The picture below shows how higher dBi antennas focus energy and transmit over longer ranges.

👉 dBi gain depends on frequency of operation and antenna factor

dBd – what does it mean?

dBd stands for decibels relative to a dipole antenna. A dipole antenna is a real, practical antenna that consists of two identical conductive elements such as metal wires or rods with a gap in between. The elements transmit or receive electromagnetic energy.

The gain of an antenna in dBd is its gain compared with the gain of a half-wave dipole antenna. Since a half-wave dipole antenna has a gain of 2.15 dBi, there’s a fixed relationship between dBi and dBd:

Gain (dBi) = Gain (dBd) + 2.15

An antenna’s gain in dBd is always 2.15 dB less than its gain in dBi because an isotropic radiator is considered to have a uniformly distributed radiation pattern, whereas a dipole has a directional pattern.

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