📡 Antenna Gain Calculator
Calculate antenna gain, EIRP, effective radiated power, and link budget for any RF system
| Antenna Type | Gain (dBi) | Gain (dBd) | Typical Beamwidth | Best Use Case |
|---|---|---|---|---|
| Isotropic (reference) | 0 dBi | −2.15 dBd | 360° all planes | Theoretical reference |
| Half-Wave Dipole | 2.15 dBi | 0 dBd | 360° H / 75° V | General-purpose, FM radio |
| Monopole / Whip | 2.0 dBi | −0.15 dBd | 360° H / 90° V | CB radio, mobile VHF/UHF |
| Fiberglass Omni | 5–8 dBi | 2.85–5.85 dBd | 360° H / 15–25° V | ISP tower, Wi-Fi sector |
| Patch / Panel | 7–9 dBi | 5–7 dBd | 60° H / 60° V | Wi-Fi AP, indoor coverage |
| Yagi 5-element | 10 dBi | 7.85 dBd | 50° H | TV reception, 900 MHz links |
| Yagi 9-element | 14 dBi | 11.85 dBd | 30° H | LTE/4G boosting, UHF |
| Yagi 17-element | 17 dBi | 14.85 dBd | 20° H | Long-range point-to-point |
| Parabolic Dish (small) | 20–24 dBi | 18–22 dBd | 8–12° | 2.4/5.8 GHz P2P links |
| Parabolic Dish (large) | 24–30 dBi | 22–28 dBd | 3–8° | Microwave backhaul |
| Frequency | 100 m | 1 km | 5 km | 10 km | 50 km |
|---|---|---|---|---|---|
| 27 MHz (CB) | 41.1 dB | 61.1 dB | 75.1 dB | 81.1 dB | 95.1 dB |
| 174 MHz (VHF) | 57.3 dB | 77.3 dB | 91.3 dB | 97.3 dB | 111.3 dB |
| 600 MHz (UHF) | 68.0 dB | 88.0 dB | 102.0 dB | 108.0 dB | 122.0 dB |
| 900 MHz (ISM) | 71.5 dB | 91.5 dB | 105.5 dB | 111.5 dB | 125.5 dB |
| 2.4 GHz (Wi-Fi) | 80.0 dB | 100.0 dB | 114.0 dB | 120.0 dB | 134.0 dB |
| 5.8 GHz (Wi-Fi) | 87.7 dB | 107.7 dB | 121.7 dB | 127.7 dB | 141.7 dB |
| 60 GHz (mmWave) | 107.0 dB | 127.0 dB | 141.0 dB | 147.0 dB | 161.0 dB |
| Standard / Band | Max TX Power | Max EIRP | Typical Antenna | Notes |
|---|---|---|---|---|
| Wi-Fi 2.4 GHz (FCC) | 30 dBm (1W) | 36 dBm | 6 dBi max | Point-to-multipoint limit |
| Wi-Fi 2.4 GHz P2P (FCC) | 30 dBm | No limit | Any (reduce TX 1:1) | Reduce 1 dBm per 3 dBi over 6 |
| Wi-Fi 5 GHz U-NII-1 | 17 dBm | 23 dBm | 6 dBi max | Indoor only |
| Wi-Fi 5 GHz U-NII-3 | 30 dBm | 36 dBm | 6 dBi | FCC Part 15 |
| 900 MHz ISM (FCC) | 30 dBm | 36 dBm | Any | Spread spectrum |
| LoRa 915 MHz (US) | 30 dBm | 36 dBm | 3–8 dBi | FCC Part 15.247 |
| CB Radio (FCC) | 4W AM / 12W SSB | N/A | Whip / Dipole | FCC Part 95 |
| Amateur (2m band) | 1500W PEP | No limit | Any licensed | Amateur license required |
| Scenario | TX Power | Antenna Gain | EIRP | Max Range (est.) |
|---|---|---|---|---|
| Home Wi-Fi Router (2.4 GHz) | 20 dBm | 2 dBi | 22 dBm | ~50–100 m indoors |
| Wi-Fi AP w/ Patch (5 GHz) | 20 dBm | 8 dBi | 28 dBm | ~100–200 m LOS |
| 900 MHz IoT Gateway | 27 dBm | 5 dBi | 32 dBm | ~5–15 km rural |
| 2.4 GHz P2P (dish) | 20 dBm | 24 dBi | 44 dBm | ~10–30 km |
| 5.8 GHz Backhaul (dish) | 23 dBm | 24 dBi | 47 dBm | ~5–15 km |
| LTE Fixed CPE | 23 dBm | 14 dBi | 37 dBm | ~10–20 km |
Antenna Gain describes whether an Antenna successfully focuses radio waves in one specific direction. Compare a torch with a ceiling lamp that spreads light through the whole space, here the key idea. A torch focuses the light in a narrow beam similarly to what Gain does with Antennas.
Here the main point: Antennas themselves do not create radio energy. They simply lead it or combine it to one course, and that combined strength is the meaning of Gain.
What Is Antenna Gain?
To go more deeply the Gain of an Antenna estimates the energy that it sends in its most strong way, compared to what a theoretical perfect Antenna would do. A perfect Antenna spreads waves equally in all directions, without any losses. Usually one writes Gain by means of decibels, and the extra letter points what base Antennas one used for the comparison.
DBi shows Gain regarding a perfect model, while dBd points comparison with a dipole Antenna.
A half-wave dipole reaches around 1.65 in Gain, but a much more short dipole, so, only 0.05 wavelengths. Comes near 1.5 during the same frequency. Dipoles focus energy quite a lot to beat the perfect base by almost 2.15 dB.
A quarter-wave vertical Antenna above ideal soil reaches a perfect 5.15 dBi, even though actual builds always lag a bit. Ground conditions, radiation patterns and growing losses commonly drop it to bewteen 2 and 5 dBi.
Here the detail: bigger Gain forces sharper focus, what strengthens the distance in the main course… So you loose reach elsewhere. That simply follows physical laws.
Antennas with high Gain shine above flat soil, because their radiation image stays clear at the horizon. Low Gain Antennas spread the signal through a wider region, what truly is useful for rough or hilly landscape.
Gain applies equally to sending and receiving. Antennas work according to mutual principle, so that advantage for sending matches that for receiving. At the receiver, Gain points how well an Antenna seizes incoming waves from a particular corner and turns them into usable energy.
If someone mentions only “Gain” without detail about course, it means the maximum level in the main beam.
Physical weight and Gain do not always match according to your expectation. A beer Antenna, for instance, beats the length of a half-wave dipole, yet gives lower Gain. Big does not always match good, at least not without conditions.
It depends on the fit between an Antenna and signal wavelength. Too large or too short elements end with bad performance.
To truly measure Gain, specialists lay an Antenna in a sound-quiet room and give it a fixed energy level. Field strength measure then circles to note values, that one compares with that of a theoretical perfect beam at the samedistance. Gain shows as the most key factor for planning Antenna systems, and one grows it by means of building the open area of an Antenna.
