Calculate antenna gain in dBi for parabolic dish, Yagi, and aperture antennas. Enter frequency, diameter, and efficiency — or estimate gain from beamwidth. Includes EIRP calculation and a full antenna type comparison table.
✓Formulas: IEEE Std 149 Antenna Gain & 3GPP / ITU-R reference data — April 2026
For parabolic dish, horn, and other aperture antennas. Enter the physical diameter (or aperture area) and operating frequency.
In GHz — e.g. 2.4 for WiFi, 5.8 for UNII-2, 12 for Ku-band satelliteEnter a valid frequency in GHz (0.001 to 100).
Physical diameter of the reflector — e.g. 0.6 m for a typical satellite dishEnter a valid diameter in meters (0.01 to 100).
Most parabolic dish designs achieve 55–65% efficiency. When in doubt, use 55%.
Antenna Gain (dBi)
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⚠️ Disclaimer: Results are theoretical estimates based on standard gain formulas. Real-world performance depends on surface accuracy, feed design, manufacturing tolerances, and environmental conditions. Verify with antenna measurement in a controlled RF environment for precision applications.
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Estimate gain for Yagi-Uda, dipole, and simple wire antennas from element count. Also converts dBi to dBd and calculates EIRP.
e.g. 0.144 for 2m HAM, 0.433 for ISM, 2.4 for WiFiEnter a valid frequency in GHz.
e.g. 20 dBm = 100 mW (WiFi); 30 dBm = 1W; 43 dBm = 20W. Leave at 20 if unsure.
Estimated Yagi Gain
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Estimate antenna gain from measured half-power beamwidths (HPBW). Useful when you have a radiation pattern but not a direct gain measurement.
Half-power (-3 dB) beamwidth in the E-plane (electric field plane)Enter E-plane beamwidth in degrees (0.1 to 180).
Half-power (-3 dB) beamwidth in the H-plane (magnetic field plane)Enter H-plane beamwidth in degrees (0.1 to 180).
Estimated Gain
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Sources & Methodology
✓Parabolic gain: G = 10×log10(η×(π×D/λ)²). Beamwidth gain: G = 10×log10(29000/(θE×θH)). EIRP = P_tx + G_dBi - L_cable. Sources: IEEE Std 149-1979, ARRL Handbook, ITU-R BS.705-1. All formulas verified April 2026.
The definitive IEEE standard defining antenna gain measurement procedures, reference antenna specifications, and the gain definitions used in this calculator. Source for the isotropic reference (dBi) and the parabolic aperture gain formula methodology.
The authoritative reference for practical antenna design, including Yagi-Uda element gain tables, dipole gain values, and aperture efficiency data for real-world antenna types. Source for the element-count-to-gain reference table in this calculator.
ITU-R recommendation documenting antenna gain characteristics, beamwidth relationships, and effective radiated power (EIRP) calculation methods referenced in this tool. Used for the gain-beamwidth relationship and EIRP formulas.
What is Antenna Gain and How Does It Work?
If you've ever wondered why satellite dishes are so much bigger than WiFi antennas, or why your long-range wireless link needs a very specific antenna, antenna gain is the answer. It's the single most important number in RF system design, and it's almost universally misunderstood.
Here's the thing most people get wrong: antenna gain does not add power. Your transmitter outputs a fixed amount of power. What the antenna does is decide where that power goes. A high-gain antenna is like a flashlight — same battery, same energy, but focused into a tight beam that's much brighter in one direction. A low-gain omnidirectional antenna is like a bare light bulb: the light spreads equally everywhere, and no single spot is very bright. Same total energy. Completely different coverage.
The Antenna Gain Formula Explained with a Real Example
Let's calculate the gain of a 60 cm satellite dish at 12 GHz (Ku-band), which is what you'd see on a typical home satellite TV installation.
G(dBi) = 10 × log10( η × (π × D / λ)² )λ = c / f = 0.3 / f_GHz (wavelength in meters)EIRP(dBm) = P_tx(dBm) + G(dBi) − Cable Loss(dB)
Worked example — 0.6 m dish at 12 GHz:
Wavelength: λ = 0.3 / 12 = 0.025 m
G_linear = 0.55 × (π × 0.6 / 0.025)² = 0.55 × (75.4)² = 0.55 × 5,685 = 3,127
G(dBi) = 10 × log10(3,127) = 34.9 dBi
That's the gain on a standard home satellite dish. With 1W transmit power (30 dBm) and 1 dB cable loss: EIRP = 30 + 34.9 − 1 = 63.9 dBm = about 2.5 kW of equivalent isotropic radiated power.
What is Antenna Gain and How Does it Work? (The Calculator Explained)
The three tabs in the calculator above cover the three most common calculation needs. The Parabolic/Aperture tab uses the standard aperture formula — enter your dish diameter and frequency and it gives you gain in dBi. Use this for satellite dishes, microwave dish antennas, and horn antennas.
The Yagi/Dipole tab estimates gain from element count using empirical relationships from antenna measurement data. Yagi gain doesn't follow a simple formula — it depends heavily on element spacing and boom length — so element-count estimates are approximations. Good for planning purposes; verify with a specific antenna model's datasheet for critical links.
The Beamwidth to Gain tab applies the classic approximate relationship G ≈ 29,000/(θE × θH). This is useful when you have a measured radiation pattern but no direct gain figure. It tends to overestimate gain slightly for antennas with high sidelobe levels.
dBi vs dBd — The Conversion That Trips Everyone Up
When you see an antenna spec, it'll quote gain as either dBi or dBd. They measure the same thing against different references. dBi is relative to an isotropic (all-directions) source. dBd is relative to a half-wave dipole. The relationship: dBi = dBd + 2.15. Always check which one your antenna uses. A "5 dBd" antenna has 7.15 dBi gain. A "5 dBi" antenna has only 2.85 dBd — which is actually slightly worse than a dipole. Getting these confused when calculating a link budget can mean the difference between a working link and a system that's 4 dB short of closing.
Antenna Gain Reference Table — All Major Antenna Types
Every RF design starts with choosing the right antenna type for the job. Gain is the primary differentiator, but it always trades against beamwidth and physical size. This table covers the realistic gain ranges for every major antenna type you're likely to encounter.
Antenna Type
Typical Gain (dBi)
Beamwidth
Common Applications
Half-wave dipole
2.15
~78° (E-plane)
Reference antenna, AM radio
Quarter-wave monopole
2.0–3.0
Omnidirectional
Car radio, cellular base stations
WiFi router (rubber duck)
2.0–5.0
Omnidirectional
Indoor WiFi, IoT devices
Patch / panel antenna
6.0–15.0
60–120°
Outdoor WiFi AP, cellular
3-element Yagi
7.0–8.5
~55°
TV reception, short-range link
5-element Yagi
9.0–10.5
~45°
HAM radio, point-to-point WiFi
10-element Yagi
12.0–13.5
~30°
Long-range WiFi, ADSB
Sector antenna (120°)
14.0–18.0
120°
WiFi hotspot, cellular BTS
Horn antenna
15.0–25.0
15–40°
Radar, microwave measurement
0.6 m parabolic dish
33.0–36.0 (at 12 GHz)
<3°
Satellite TV (Ku-band)
1.0 m parabolic dish
32.0–35.0 (at 5 GHz)
<2°
Point-to-point microwave link
1.8 m parabolic dish
38.0–42.0 (at 12 GHz)
<1.5°
Satellite uplink, commercial
Large radar dish (5 m)
45.0–55.0
<0.5°
Air traffic control, weather radar
The most important thing this table shows: as gain increases, beamwidth shrinks relentlessly. A 10 dBi antenna has a comfortable 40 to 50 degree beam that's easy to aim. A 35 dBi dish has a 1 to 2 degree beam where even a small mount shift causes significant signal loss. This is why satellite dish alignment is so fussy — you're trying to hit a tiny window in the sky with a very narrow spotlight.
What Antenna Gain Do You Actually Need? A Practical Decision Guide
Buying the highest-gain antenna you can find sounds like a good idea — more gain, better signal, right? Not always. Picking the wrong gain level is one of the most common mistakes in wireless link design, and it goes both ways. Too little gain and your link doesn't close. Too much gain and you spend the next three hours trying to aim a 1-degree beam at a target you can't see.
WiFi and Indoor Wireless
For indoor WiFi access points, 2 to 5 dBi omnidirectional antennas are almost always the right choice. They provide coverage in all directions, which is what you need when you don't know where devices will be. Putting a 15 dBi directional antenna on an indoor AP only serves one corner of the room. For outdoor point-to-point WiFi under 500 meters — like bridging two buildings — a 10 to 15 dBi patch antenna on each end is plenty. Beyond 1 km, you need 20 to 25 dBi and precise alignment.
HAM Radio and Amateur Applications
For HF and VHF HAM radio, antenna gain is often secondary to EIRP limits and antenna directivity patterns. A 5-element Yagi at 144 MHz (2m band) provides about 10 dBi gain with a reasonably wide beam for terrestrial use. For weak-signal work and EME (Earth-Moon-Earth) communications, HAM operators build 16 to 20+ element Yagis or arrays of multiple antennas, reaching 18 to 25 dBi. The ARRL has specific recommendations for different HAM applications.
Satellite and Microwave Links
Satellite links need the most gain. Ku-band home satellite dishes (0.6 to 0.9 m) at 11 to 12 GHz achieve 34 to 40 dBi. Larger commercial uplink dishes reach 45 to 50 dBi. Microwave point-to-point backhaul links at 18 GHz typically use 0.3 to 0.6 m dishes achieving 30 to 36 dBi — enough for a reliable 10 km link with appropriate transmit power.
💡 The gain-beamwidth tradeoff in practice: An engineer speccing a 10 km WiFi link chose a 30 dBi dish antenna for maximum gain. Installation was a nightmare — the 1.5-degree beam had to be aligned with sub-degree precision between two buildings that both moved slightly with temperature. A pair of 24 dBi dishes with their wider 4-degree beam would have closed the link with 6 dB margin to spare and taken 20 minutes to align instead of half a day. Match your gain to the geometry, not to the maximum available.
EIRP Limits — The Regulatory Constraint
Antenna gain is regulated, not transmit power alone. Most regulatory bodies limit EIRP (Effective Isotropic Radiated Power), which is transmit power plus antenna gain minus cable losses. FCC limits for unlicensed bands: 2.4 GHz WiFi = 36 dBm EIRP maximum. 5 GHz WiFi = 30 dBm EIRP. If you're running 23 dBm (200 mW) at 2.4 GHz, you're already allowed up to 13 dBi of antenna gain before hitting the EIRP limit. Exceeding EIRP limits with a high-gain antenna — even accidentally — puts you outside regulatory compliance.
⚠️ Common mistake: Adding a high-gain antenna to a WiFi router without reducing transmit power. Many routers run at 20 to 23 dBm. Adding a 20 dBi antenna brings EIRP to 40 to 43 dBm — well above FCC limits. If you add a high-gain antenna to a WiFi device, you may need to reduce transmit power accordingly to stay compliant.
Frequently Asked Questions
Antenna gain measures how well an antenna focuses radio energy in a specific direction compared to an isotropic radiator. Expressed in dBi, it doesn't add power — it focuses existing transmitter power. A 10 dBi antenna makes the signal 10 times stronger in its main direction than a perfect omnidirectional source. Think of a flashlight versus a bare bulb: same battery, very different brightness in any one direction.
For parabolic/aperture antennas: G(dBi) = 10 × log10(η × (π×D/λ)²), where η is efficiency (0.55–0.65), D is diameter in meters, and λ = 0.3/f_GHz. For beamwidth estimation: G(dBi) = 10 × log10(29000/(θE × θH)). Worked example: 1m dish at 5 GHz with 60% efficiency gives G = 10 × log10(0.60 × (π×1/0.06)²) = 34.2 dBi.
dBi is gain relative to an isotropic radiator (theoretical, all-directions). dBd is gain relative to a half-wave dipole. Conversion: dBi = dBd + 2.15. A 5 dBd antenna has 7.15 dBi. A 5 dBi antenna has only 2.85 dBd. Always check which reference your antenna spec uses before doing link budget calculations. Confusing them introduces a 2.15 dB error that can make or break a marginal link.
For indoor access points: 2 to 5 dBi omnidirectional. For outdoor point-to-multipoint: 10 to 18 dBi sector or patch. For point-to-point links under 1 km: 20 to 24 dBi. For links from 1 to 10 km: 24 to 30 dBi parabolic. Remember the EIRP limit: FCC caps 2.4 GHz at 36 dBm EIRP. At 23 dBm transmit power, you can use up to 13 dBi before hitting the limit. Going higher requires reducing transmit power.
No. Antenna gain never adds power. It redirects the transmitter's existing power into a narrower beam, increasing signal strength in that direction. EIRP (Effective Isotropic Radiated Power) = transmit power + antenna gain − cable losses. EIRP can be large, but the actual radiated power is always equal to or less than what the transmitter outputs (minus losses).
EIRP (Effective Isotropic Radiated Power) is the total power an isotropic antenna would need to radiate to produce the same signal in the main beam. EIRP (dBm) = Transmit Power (dBm) + Antenna Gain (dBi) − Cable Loss (dB). Example: 20 dBm + 15 dBi − 2 dB = 33 dBm EIRP. The FCC limits 2.4 GHz unlicensed devices to 36 dBm EIRP.
Aperture efficiency (η) is the ratio of effective to physical aperture, from 0 to 1. Real antennas lose efficiency from illumination taper, feed spillover, blockage, and surface errors. Typical values: standard parabolic dish 55 to 65%, precision horn 70 to 90%, patch antenna 50 to 60%. When in doubt, use 55% for parabolic dishes — it gives a realistic conservative estimate and matches most published datasheet gains within 1 to 2 dB.
Higher gain always means narrower beamwidth — there's no avoiding this tradeoff. A 10 dBi antenna has roughly a 50 to 60 degree beamwidth. A 20 dBi antenna narrows to about 10 degrees. A 30 dBi dish is under 3 degrees. This is why high-gain dishes require precise mechanical alignment and why omnidirectional antennas have such low gain: you can't focus energy in all directions at once.
A Yagi's gain scales with element count. Dipole alone: 2.15 dBi. 3 elements: 7 to 8 dBi. 5 elements: 9 to 10 dBi. 10 elements: 12 to 13 dBi. 15 elements: 14 to 15 dBi. Beyond 20 elements, gains rarely exceed 17 to 18 dBi due to diminishing returns. Exact gain also depends on element spacing and boom length — these estimates are good for planning but verify against specific antenna datasheets for precise link budgets.
2.15 dBi. A half-wave dipole is the reference antenna for dBd measurements: 0 dBd = 2.15 dBi. It produces a slightly flattened toroidal radiation pattern — not perfectly omnidirectional, stronger broadside and weaker off the ends. Most simple WiFi router antennas are half-wave dipoles achieving 2 to 3 dBi. Any antenna exceeding 2.15 dBi outperforms a dipole in its best direction.
G(dBi) = 10 × log10(G_linear). If your antenna is 100 times stronger in its main direction than an isotropic source: G = 10 × log10(100) = 20 dBi. Reverse: G_linear = 10^(G_dBi/10). A 15 dBi antenna has linear gain 10^(15/10) = 31.6 — meaning its signal is 31.6 times stronger than an isotropic source in its beam direction.
A 60 cm dish at 12 GHz (Ku-band satellite): ~34 to 37 dBi. A 1 m dish at 5 GHz: ~32 to 35 dBi. A 1.8 m dish at 12 GHz: ~40 to 43 dBi. Gain scales strongly with both size and frequency: doubling diameter adds ~6 dBi, doubling frequency adds ~6 dBi. Practical dish efficiency is 55 to 65% — use the calculator above to get exact values for your specific parameters.
Indoor WiFi: 2 to 5 dBi omnidirectional. Cellular BTS sector: 14 to 18 dBi. Point-to-point WiFi 1–5 km: 23 to 28 dBi. Ku-band satellite dish: 34 to 45 dBi. Radar: 35 to 55 dBi. Radio astronomy (large arrays): 50 to 80+ dBi. The pattern is clear: longer links and weaker signals require more gain, which requires larger antennas and more precise alignment.