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Wireless & Mobility · Foundational

Decibel Relative to Isotropic Radiator (dBi)

Antenna gain in decibels compared with a theoretical isotropic radiator.

Definition

dBi measures how much an antenna focuses energy in a given direction compared with a perfect isotropic radiator that radiates equally in all directions. Antennas do not add energy; gain comes from reshaping the radiation pattern. Most Wi-Fi antenna specifications use dBi.

Example

A typical indoor omni antenna is rated 2 to 5 dBi.

Exam tip

0 dBd equals 2.14 dBi; convert by adding 2.14 to a dBd value.

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