Antenna Gain to Beamwidth Calculator

About this calculator

For a symmetric, pencil-beam antenna, the half-power (−3 dB) beamwidth can be estimated from gain alone using a standard empirical approximation, roughly θ ≈ √(52525 / G_linear) degrees, where the gain in dBi is first converted to a linear ratio. Higher gain concentrates energy into a narrower beam, so this relationship trades off coverage angle against signal strength in one direction — it's an approximation because true beamwidth also depends on the antenna's exact aperture shape and efficiency.

RF and wireless network engineers use this trade-off when choosing between a high-gain, narrow-beam antenna and a lower-gain, wide-coverage one for a given site, satellite and point-to-point link technicians use estimated beamwidth to judge how precisely a dish needs to be aimed, and WiFi and cellular site planners use it to predict a sector antenna's coverage footprint.