Antenna Beamwidth Estimate Calculator

How it is calculated

Enter the antenna gain in dBi (between 0 and 60; values outside that range give no result). Step 1 converts decibels to a plain ratio: G = 10^(gain ÷ 10). Step 2 estimates the half-power beamwidth: HPBW = √(41253 ÷ G) degrees. The number 41253 is roughly the count of square degrees on a full sphere, and the formula treats the main beam as equally wide in both planes, so it suits dishes and similar symmetric antennas, not a sector antenna that is wide in one plane and narrow in the other. It also assumes the gain is concentrated in that beam with no losses. Both the beamwidth and G are shown with two decimals.

Common mistakes

• Entering gain in dBd or as a plain ratio: the field is dBi, and a dipole's 2.15 dBi is not the same as 0 dBd.
• Applying the result to a sector or panel antenna with different horizontal and vertical beams: the formula gives one equal-in-both-planes angle.
• Trusting the result at very low gains: near 0 dBi the angle comes out at 200 degrees or more, which cannot be a real beamwidth.
• Confusing half-power beamwidth with the full angle of radiation: HPBW is the width between the −3 dB points, and energy still leaves outside it.
• Treating the estimate as the datasheet value: real antennas have sidelobes, losses and unequal planes, so use it for planning and not for pointing tolerances.