Antenna Gain Calculator - Free Online Calculator | How is Antenna Gain Calculated?

Antenna Gain Calculator

The calculator developed by us will give the antenna gain as the combination of the electrical efficiency and the antenna’s directivity of an isotropic source. And this antenna gain can be found easily if the wavelength, efficiency, and physical aperture are provided as the input by the user.

The term Antenna Gain in physics describes how much power is transmitted in the direction of peak radiation to that of an isotropic source in which the nature of the source is considered to be neutral. Antenna gain is more commonly quoted than directivity in an antenna's specification sheet because it takes into account the actual losses that occur in the overall system.

What is Meant by Antenna Gain?

A transmitting antenna with a gain of 3 dB of an isotropic source in which the nature of the source is considered to be neutral means that the power received far from the antenna will be 3 dB higher (twice as much) than what would be received from a lossless isotropic antenna with the same input power as that of an isotropic source. The lossless antenna would be an antenna with an antenna efficiency of 0 dB (or 100%). Similarly, a receive antenna with a gain of 3 dB in a particular direction would receive 3 dB more power than a lossless isotropic antenna in any such case.

In Physics, The symbol used to represent the antenna gain of an isotropic source is “dB”. We know that “dB” is the measurement unit of the loss or gain. The formula to calculate the antenna gain is given by:

Antenna Gain, GdBi  = 10 log10 (η4πA/λ2)

  • Where A is the physical aperture area
  • η is the efficiency
  • λ is the wavelength.

Effective Aperture

When an electromagnetic wave that is created as a result of vibrations between an electric field and a magnetic field following the direction of the propagation is transmitted by the transmitting antenna then the receiving antenna present at the other end tries to capture the emitted radiation in the same direction. The antenna aperture is associated with the act of receiving antenna as it tells about the extracting ability of the antenna that is concerned with the reception of the waves in the same medium.

The effective aperture of an antenna is referred to as that region of the receiving antenna that effectively collects the electromagnetic energy from the radiated wave out of the overall antenna region. This means the greater the extracting region of the antenna more efficient it is the propagating plane.

Units of Antenna Gain

If you look at the specification sheet for an antenna, you will typically see units for antenna gain listed in dB, dBi, or dBd. 

  • dB - decibels. 10 dB means 10 times the energy relative to an isotropic antenna in the peak direction of radiation.
  • dBi - "decibels relative to an isotropic antenna in the wave propagation". This is the same as dB as we have been using it. 3 dBi means twice (2x) the power relative to an isotropic antenna in the peak direction.
  • dBd - "decibels relative to a dipole antenna in the isotropic wave propagation". Note that a half-wavelength dipole antenna has a gain of 2.15 dBi. Hence, 7.85 dBd means the peak gain is 7.85 dB higher than a dipole antenna; this is 10 dB higher than an isotropic antenna.
Antenna Factor and Gain Calculations

Solved Examples of Antenna Gain

Example 1:

Calculate the Antenna Gain for the Efficiency (η) = 5, Wave Length (λ) = 10, Physical Aperture Area (A) = 15 of the wave traveling in isotropic propagation.


Subsitutuing th evalues in the Formula:

GdBi = 10 LOG10 ( η4πA / λ2)

GdBi = 9.74271

Antenna Gain (GdBi) = 9.74271

In addition to the antenna gain calculator you can find plenty of physics concepts belonging to classical mechanics, electromagnetism, waves, optics all under one roof at

FAQs on Antenna Gain Calculator

1. How is antenna gain calculated?

Gain is calculated by comparing the measured power transmitted or received by the antenna in a specific direction to the power transmitted in an isotopic medium or received by a hypothetical ideal antenna in the same situation.

2. What is the significance of the beamwidth of the antenna?

The Importance of Antenna Beamwidth in RF Testing. Antenna beamwidth determines the expected signal strength given the direction and radiation distance of an antenna from the initial position of the bandwidth.

3. What is dB in the antenna?

dB is antenna gain in decibels reference to how much times gain increase there is with respect to 1(0dB). 

4. What is the aperture of an antenna?

The aperture of the antenna in the area whose orientation is normal to the direction from where the electromagnetic wave is coming in the direction of propagation.

5. What is a half-wave dipole?

A half-wave antenna (referred to as a dipole, Hertz, or doublet) consists of two lengths of wire rod, or tubing, each 1/4 wavelength long at a certain frequency similar to that of the antenna.