Dipole length chart for every HF band

Cut three percent long, hang it at final height, then trim.

The short answer

A half wave dipole in feet is approximately 468 divided by the frequency in megahertz, so a 40 metre dipole at 7.15 MHz is 65 ft 5 in overall, with each leg 32 ft 9 in. Cut three percent long and trim after measuring at final height, because height and nearby objects both shift resonance downward.

Half wave formula: 468 / f in MHz
Quarter wave formula: 234 / f in MHz
Start long by: 3 percent
Trim rule: 1 percent length, 1 percent frequency
Measure at: Final height
Insulated wire: Cut 2 to 4 percent shorter

These are the cut lengths for the three antenna types most people build: a centre fed half wave dipole, a quarter wave vertical, and an end fed half wave. The formula behind all of them is the same, and the figures already include the velocity factor of wire near ground, which is why the constant is 468 rather than 492.

Treat every number here as a starting point. Height above ground, wire insulation, the angle of an inverted V and anything metal nearby all shift resonance, almost always downward. Cut long, hang it, measure, then trim.

Lengths by band

Cut lengths

Half wave, dipole leg and quarter wave by band

Band and frequency	Half wave total	Each dipole leg	Quarter wave
160 m, 1.900 MHz	246 ft 4 in	123 ft 2 in	123 ft 2 in
80 m, 3.600 MHz	130 ft 0 in	65 ft 0 in	65 ft 0 in
80 m, 3.800 MHz	123 ft 2 in	61 ft 7 in	61 ft 7 in
60 m, 5.357 MHz	87 ft 4 in	43 ft 8 in	43 ft 8 in
40 m, 7.050 MHz	66 ft 5 in	33 ft 2 in	33 ft 2 in
40 m, 7.200 MHz	65 ft 0 in	32 ft 6 in	32 ft 6 in
30 m, 10.125 MHz	46 ft 3 in	23 ft 1 in	23 ft 1 in
20 m, 14.100 MHz	33 ft 2 in	16 ft 7 in	16 ft 7 in
20 m, 14.250 MHz	32 ft 10 in	16 ft 5 in	16 ft 5 in
17 m, 18.110 MHz	25 ft 10 in	12 ft 11 in	12 ft 11 in
15 m, 21.100 MHz	22 ft 2 in	11 ft 1 in	11 ft 1 in
15 m, 21.300 MHz	22 ft 0 in	11 ft 0 in	11 ft 0 in
12 m, 24.940 MHz	18 ft 9 in	9 ft 5 in	9 ft 5 in
10 m, 28.400 MHz	16 ft 6 in	8 ft 3 in	8 ft 3 in
10 m, 29.000 MHz	16 ft 2 in	8 ft 1 in	8 ft 1 in
6 m, 50.150 MHz	9 ft 4 in	4 ft 8 in	4 ft 8 in
2 m, 146.000 MHz	3 ft 2 in	1 ft 7 in	1 ft 7 in

For any frequency not listed, use the dipole length calculator or the quarter wave vertical calculator. For an end fed, the wire is the half wave figure and the end fed half wave calculator covers the counterpoise as well.

End fed half wave lengths

An end fed half wave uses the same total length as a dipole but is fed at one end through a 49 to 1 transformer. Because it is close to resonant on even harmonics, one wire covers several bands.

End fed

Multiband coverage from one wire

Design band	Wire length	Also covers	Counterpoise
80 m	About 130 ft	40, 20, 15, 10 m	About 6 ft 6 in
40 m	About 66 ft	20, 15, 10 m	About 3 ft 3 in
20 m	About 33 ft	10 m	About 1 ft 8 in
30 m	About 46 ft	15 m	About 2 ft 4 in

The counterpoise figure is roughly 0.05 wavelengths on the design band. It is not optional. Without it the antenna uses the outside of your coax braid as the counterpoise, which puts RF in the shack. Fit a choke as well.

Trimming

Trim amounts

Wire to remove to move resonance up by a given amount

Band	Half wave	Up 50 kHz	Up 100 kHz	Up 200 kHz
80 m at 3.7 MHz	126 ft 6 in	20 in	41 in	82 in
40 m at 7.1 MHz	65 ft 11 in	5.5 in	11 in	22 in
30 m at 10.1 MHz	46 ft 4 in	2.8 in	5.5 in	11 in
20 m at 14.15 MHz	33 ft 1 in	1.4 in	2.8 in	5.6 in
17 m at 18.1 MHz	25 ft 10 in	0.9 in	1.7 in	3.4 in
15 m at 21.2 MHz	22 ft 1 in	0.6 in	1.3 in	2.5 in
10 m at 28.4 MHz	16 ft 6 in	0.4 in	0.7 in	1.4 in

On a centre fed dipole, split the figure across both legs. On an end fed, take the whole amount from the far end. Take half your calculated cut on the first pass, because you cannot easily put wire back. Full method in how to tune an antenna with an SWR meter.

What shifts these numbers

Height above ground. A dipole at a quarter wavelength resonates lower than the same dipole at half a wavelength. Always measure at final height.
Insulated wire. Insulation slows the wave, so an insulated wire is 2 to 4 percent shorter than a bare one for the same resonance.
Inverted V angle. Drooping the ends lowers resonance and lowers the feedpoint impedance. A 120 degree included angle is a common compromise.
Nearby metal. Gutters, fences, mast sections and other antennas all couple capacitively and pull resonance down.
End effect. Already accounted for in the 468 constant, which is why the constant is not the free space 492.
Wire diameter. Thicker conductors are slightly shorter for the same resonance and have wider bandwidth, which is why fat elements are used on beams.

What to build it from

Wire, rope and hardware

The whole antenna is inexpensive. The rope is what decides how long it lasts.

XRDS-RF

XRDS-RF 14 AWG stranded copper wire, 25 ft

Stranded insulated wire that survives being pulled into a tree and left there for years.

Check price$14.99

Paladin

Paladin 14 AWG stranded copper wire, 500 ft

A larger spool for building several antennas or a radial field.

Check price$74.50

Quality Nylon Rope

QNR 3/16 in polyester antenna rope, 500 ft

UV-stable, low-stretch support rope. The single component that decides whether the antenna survives a season.

Check price$49.73

Redman

Nylon dog bone antenna insulators, 10-pack

End insulators so the high-voltage wire tips terminate into rope rather than into a branch.

Check price$29.97

GOOZEEZOO

GOOZEEZOO 150 W end fed antenna transformer

A 49 to 1 transformer for building an end fed from your own wire.

Check price$29.90

Fair-Rite type 31

FT-240-31 ferrite toroid core

A ferrite core for the common mode choke that every wire antenna installation needs.

Check price$11.67

Forester

Forester arborist throw line kit

Getting the support line over a branch, which is the actual hard part.

Check price$21.99

AURSINC

NanoVNA H4 vector network analyzer

Shows where the antenna is resonant, which turns four trips outside into one.

Check price$89.90

Safety

Never raise an antenna where it can reach a power line

Contact with an overhead power line kills amateur operators every year. It is the most common fatal accident in this hobby by a wide margin, and it happens during the raising, not during operation.

Before any antenna work, walk the site and find every overhead conductor, including the service drop to your own house. Assume the antenna, the mast, the support rope and the person holding it can all fall in any direction. If any part of the installation could contact a line while being raised, lowered, or blown down later, do not put it there. Move the antenna, not the risk.

A wire antenna launched into a tree can drift into a line. A telescoping mast can be dropped. A guy rope can be walked into a service drop in the dark. There is no version of this where a power line nearby is acceptable.

Antenna and mast installation safety

Common questions

Questions people ask about this

How long is a 40 metre dipole?

About 65 ft 5 in overall at 7.15 MHz, which is 32 ft 9 in per leg. That figure comes from 468 divided by the frequency in megahertz and already includes the end effect that makes a real wire shorter than a free space half wave. Cut about three percent long, hang it at final height, measure the resonance and then trim.

Why is the constant 468 rather than 492?

A half wavelength in free space in feet is 492 divided by the frequency in megahertz. A real wire near ground is electrically longer than its physical length because of end effect and the velocity factor of a conductor with finite diameter, so the physical length needed for resonance is shorter. The 468 constant absorbs that correction and works well for typical amateur wire.

Do I cut the same length for insulated and bare wire?

No. Insulation slows the wave slightly, so an insulated wire resonates lower than a bare wire of the same length and needs to be about two to four percent shorter. The practical approach is identical either way: cut long, measure the actual resonance at final height, and trim, since the exact factor depends on the specific insulation.

Does it matter if my dipole is an inverted V?

It works well and it changes the numbers slightly. Drooping the ends lowers the resonant frequency and lowers the feedpoint impedance, so an inverted V typically needs to be a little shorter than a flat top and often shows a better match to 50 ohm coax. It also needs only one high support point, which is why so many people build them.

How do I know if my antenna is too long or too short?

Sweep it with an antenna analyser and find the frequency of minimum SWR. If that frequency is below the band you want, the antenna is too long and needs trimming. If it is above, the antenna is too short and needs wire added. A single SWR reading at one frequency cannot tell you which, which is why an analyser is the tool that saves trips outside.

Keep going

Related on this site

Keeping your own cut lengths, SWR sweeps and exposure record? The Station Build & Antenna Planner is the paid version of these pages: 8 printable worksheets you fill in with your own numbers, plus the full PDF, $29.

Disclaimer Researched guidance for planning purposes, not professional engineering, electrical or legal advice. Antenna work, RF exposure, mast and tower work, grounding and battery handling all carry real risk that depends on your specific site and installation. Verify anything safety-critical against current FCC rules, the National Electrical Code and the manufacturer's own documentation, and hire a professional where the job calls for one. We research equipment from published specifications, regulatory documents and verified owner reviews rather than claiming hands-on testing we have not done.