Antenna Gain & Beamwidth Calculator
A quick, shape-agnostic aperture calculator — enter an aperture size to get gain and beamwidth, or flip it around and solve for the aperture size you need to hit a target gain or beamwidth. Works for circular (dish), square (panel/array) and rectangular (horn-like) apertures.
This page is a fast, shape-agnostic sizing tool. For the physical design of a specific antenna, or the exact rotate-and-cut radiation pattern, use one of these:
Antenna Gain and Beamwidth
For any aperture antenna — a parabolic dish, a flat panel array, a horn — gain and beamwidth are two sides of the same coin: both come from the same physical aperture area relative to the wavelength. A bigger aperture (in wavelengths) always means higher gain and a narrower beam; you cannot get one without the other from a single aperture. Gain follows G = η·4πA/λ², where A is the physical area and η is the aperture efficiency (typically 0.5–0.65 for real dishes and horns once spillover, blockage and phase errors are accounted for). Beamwidth follows the rule-of-thumb HPBW ≈ k·λ/D, where the constant k depends on how the aperture is illuminated — k ≈ 58° for a theoretical uniformly-illuminated aperture, rising to k ≈ 70° for the tapered illumination typical of a real fed reflector, which trades a slightly wider beam for much lower sidelobes.
Why solve backwards from gain or beamwidth?
Link budgets and system requirements are usually specified as a gain target (say, 24 dBi for a WiFi panel) or a coverage requirement expressed as a beamwidth (say, a 20° sector). Sizing the aperture directly — "how big does my dish need to be to hit 40 dBi at 12 GHz" — saves the round-trip of guessing a diameter, computing gain, and iterating by hand.