A ham radio antenna length calculator computes the correct physical dimensions for dipole and vertical antennas based on operating frequency. Getting the length right ensures the antenna resonates at your target frequency — a correctly sized antenna means better radiation efficiency, lower SWR, and no need for an antenna tuner. Use band presets or enter any frequency in the HF, VHF, or UHF range.
Antenna Parameters
Enter any frequency between 0.1 and 1000 MHz
Results
All Band Lengths (Half-wave Dipole)
| Band | Freq (MHz) | Total Length | Each Element |
|---|
How to Calculate Ham Radio Antenna Length
Antenna resonance is fundamental to amateur radio. A correctly sized antenna is more efficient, presents a better impedance match to the feedline, and requires less power to make contacts. The ham radio antenna length calculator uses the standard engineering formulas with a practical velocity factor for real-world wire antennas.
Step 1: Select a Band or Enter Your Frequency
Choose a band preset (160m through 70cm) and the calculator fills in the center frequency for that band. Alternatively, type any frequency directly in the MHz field. Use the exact frequency you plan to operate on for the best resonance — for example, 14.225 MHz for the SSB portion of 20m, or 7.040 MHz for 40m CW.
Step 2: Choose Your Antenna Type
Three types are supported: half-wave dipole (most common, fed in the center), quarter-wave vertical (single element, needs a ground plane), and Yagi element (driven or director element for beam antennas). The dipole formula is 468 / frequency (MHz) for total length. The quarter-wave vertical uses 234 / frequency (MHz).
Step 3: Toggle Between Imperial and Metric
North American hams typically measure wire in feet and inches. European and other operators prefer meters and centimeters. Toggle the unit switch to see results in your preferred measurement system.
Step 4: Cut Long and Trim to Resonance
Always cut your antenna wire about 5% longer than the calculated length. Measure SWR at your operating frequency, then trim a little at a time from each end until you reach minimum SWR. This trims-to-resonance approach is more reliable than trusting raw calculations alone, since real-world factors (wire diameter, nearby objects, height above ground) all affect the exact resonant frequency.
Band Comparison Table
The table at the bottom of the tool shows precomputed lengths for all major amateur radio bands. Use it as a quick reference when planning which band to target based on the space available in your yard or attic. A 20m dipole is about 33 feet end-to-end — manageable for most homes. A 160m dipole is 246 feet, requiring a large property or a different antenna type such as a shortened vertical with loading coil.
FAQ
Is this ham radio antenna calculator free?
Yes, completely free with no signup required. All calculations happen instantly in your browser.
What is the formula for a half-wave dipole?
The standard formula is: length (feet) = 468 / frequency (MHz). This accounts for a velocity factor of approximately 0.95, giving a practical length slightly shorter than the theoretical half wavelength. In metric: length (meters) = 142.65 / frequency (MHz).
What is the formula for a quarter-wave vertical?
Quarter-wave vertical length (feet) = 234 / frequency (MHz), which is exactly half the dipole length. In metric: 71.32 / frequency (MHz). Verticals require a ground plane or radials to complete the antenna system.
Which antenna type is best for HF ham radio?
For general use, a half-wave dipole is the most common first antenna — simple, effective, and can be fed with coax. Quarter-wave verticals work well when you cannot get height, since they are shorter and can be mounted low. Yagi elements are for directional work on VHF/UHF bands.
Why does antenna length differ from wavelength?
A theoretical half-wavelength is the speed of light divided by twice the frequency. In practice, wire antennas have an end effect that shortens the resonant length slightly. The constant 468 (instead of 492) accounts for this velocity factor (~0.95 for typical wire).
What band presets are available?
The calculator includes presets for all major amateur radio HF bands: 160m, 80m, 40m, 30m, 20m, 17m, 15m, 12m, 10m, and VHF/UHF bands 6m, 2m, and 70cm. Each preset uses the band center frequency by default.