Antenna Size Calculator
Enter the frequency and choose the antenna type. The calculator gives the antenna length, the length of each dipole leg or the radials, and the wavelength.
- Antenna length
- Each leg
- Wavelength
Cut it a little long and trim to tune with an SWR meter.
A half wave dipole is 468 ÷ frequency in MHz feet long. For 14.2 MHz on the 20 m band, a dipole is about 32.96 ft, two legs of 16.48 ft. A quarter wave vertical is half that, 16.48 ft, with radials.
Dipole length chart
Ham bands. Search for a band.
| Band | Frequency (MHz) | Dipole (ft) | Each leg (ft) | Quarter wave (ft) |
|---|---|---|---|---|
| 160 m | 1.9 | 246.32 | 123.16 | 123.16 |
| 80 m | 3.75 | 124.8 | 62.4 | 62.4 |
| 40 m | 7.15 | 65.45 | 32.73 | 32.73 |
| 30 m | 10.12 | 46.25 | 23.12 | 23.12 |
| 20 m | 14.2 | 32.96 | 16.48 | 16.48 |
| 17 m | 18.12 | 25.83 | 12.91 | 12.91 |
| 15 m | 21.2 | 22.08 | 11.04 | 11.04 |
| 12 m | 24.94 | 18.77 | 9.38 | 9.38 |
| 10 m | 28.4 | 16.48 | 8.24 | 8.24 |
| 6 m | 50.1 | 9.34 | 4.67 | 4.67 |
| 2 m | 146 | 3.21 | 1.6 | 1.6 |
Feet.
Frequency and dipole
Half wave dipole. Slide the frequency.
The dipole shortens as frequency rises.
How to size an antenna
Frequency to length. Step through it.
Frequency
MHz.
Mount dipoles as high and clear as you can.
Dipole, quarter wave or 5/8 wave
Antenna types. Compare them.
Wire.
Vertical.
Vertical.
Verticals need radials or a ground plane to work well.
Before you cut
Antenna checks. Tick each item.
Tick each item as you go.
Check local rules and your licence before transmitting.
What you get
Antenna sizing. Each tile explains one result.
Feet and metres.
Each side.
Metres.
Named.
Tips.
Insulated wire is slightly slower, so it may need trimming shorter.
Frequently Asked Questions
No question matches that search.
How long should a dipole be?
About four hundred and sixty eight divided by the frequency in megahertz, in feet.
How long is a twenty metre dipole?
About thirty three feet in total.
How long is a quarter wave antenna?
About two hundred and thirty four divided by the frequency in megahertz, in feet.
Why is a dipole shorter than half a wavelength?
End effects and the wire's thickness make it resonate about five per cent short.
Do I need radials?
Vertical antennas do. Dipoles do not.
How do I tune a dipole?
Trim both ends evenly until the SWR is lowest at your frequency.
Does higher frequency mean a shorter antenna?
Yes. Double the frequency halves the length.
Resonant on the first try
Cut your antenna to the right length and spend your time on the air, not trimming wire.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.