Receive Antenna Gain Calculator
The receive antenna gain calculator determines how much a receive antenna amplifies incoming radio signals in the desired direction, expressed in dBi or dBd. Antenna gain is a critical parameter in wireless link budgets, satellite communications, radar design, and Wi-Fi network planning. Unlike electronic amplifiers, antenna gain is passive - it works by shaping the radiation pattern to focus energy in preferred directions at the expense of other directions. This calculator supports two methods: aperture-based gain (for parabolic dishes, horn antennas, and phased arrays) and direct unit conversion between dBi, dBd, and linear gain. Enter the operating frequency, aperture area, and efficiency for the aperture method, or simply enter a known gain value to convert between units.
Antenna gain formula
Aperture: G = (4 * pi * A * eta) / lambda^2
G(dBi) = 10 * log10(G)
G(dBd) = G(dBi) - 2.15
lambda = c / f (c = 3e8 m/s)
Typical antenna gains
- Isotropic radiator (theoretical): 0 dBi
- Half-wave dipole: 2.15 dBi
- Quarter-wave monopole: 5.19 dBi
- Yagi-Uda (6 elements): ~10 dBi
- Small parabolic dish (0.6 m at 2.4 GHz): ~20 dBi
- Large satellite dish (3 m at 12 GHz): ~50 dBi
Antenna gain: frequently asked questions
What is antenna gain?
Antenna gain measures how well an antenna focuses radio energy in a specific direction compared to a reference antenna. It is expressed in dBi (relative to an isotropic radiator) or dBd (relative to a half-wave dipole). Gain does not mean the antenna amplifies signals - it directs energy more efficiently in a preferred direction.
What is the difference between dBi and dBd?
dBi measures gain relative to a theoretical isotropic antenna that radiates equally in all directions. dBd measures gain relative to a half-wave dipole. A dipole has 2.15 dBi of gain, so dBi = dBd + 2.15. Manufacturers often specify gain in dBd to make figures appear smaller.
How does aperture area relate to antenna gain?
For aperture antennas (dishes, horns, arrays): G = (4 * pi * A * eta) / lambda^2. Where A is physical aperture area, eta is efficiency (typically 0.5 to 0.8), and lambda is wavelength. Larger apertures and shorter wavelengths (higher frequencies) give more gain.
What is effective isotropic radiated power (EIRP)?
EIRP = transmit power (dBm) + antenna gain (dBi) - cable loss (dB). It represents the equivalent power that an isotropic antenna would need to radiate to produce the same signal strength at the receiver. EIRP is the key metric for regulatory compliance and link budget calculations.
How is antenna gain related to beamwidth?
Gain and beamwidth are inversely related. A high-gain antenna has a narrow beamwidth, concentrating energy in a small angular region. A rough approximation: G ≈ 32,400 / (theta_az * theta_el), where theta values are the half-power beamwidths in degrees in azimuth and elevation planes.
Official sources
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.