Dipole & Antenna Length Calculator (Feet and Metres)
Half-wave dipole, quarter-wave vertical and full-wave loop lengths for any frequency, in feet and metres.
Formulas used
- Half-wave dipole, total length:
468 ÷ f(MHz)feet (142.6 ÷ fmetres) - Quarter-wave vertical or radial:
234 ÷ f(MHz)feet - Full-wave loop, total wire:
1005 ÷ f(MHz)feet
These are the classic starting points for wire antennas. Height, nearby objects, wire insulation and the feedpoint all shift resonance, so cut the wire a few percent long and trim it while watching SWR.
Lengths for every band
| Band | MHz | Dipole total | Each leg | ¼-wave vertical | Full-wave loop |
|---|---|---|---|---|---|
| 160m | 1.9 | 246.3 ft / 75.08 m | 123.2 ft / 37.54 m | 123.2 ft / 37.54 m | 528.9 ft / 161.22 m |
| 80m | 3.75 | 124.8 ft / 38.04 m | 62.4 ft / 19.02 m | 62.4 ft / 19.02 m | 268.0 ft / 81.69 m |
| 60m | 5.357 | 87.4 ft / 26.63 m | 43.7 ft / 13.31 m | 43.7 ft / 13.31 m | 187.6 ft / 57.18 m |
| 40m | 7.15 | 65.5 ft / 19.95 m | 32.7 ft / 9.98 m | 32.7 ft / 9.98 m | 140.6 ft / 42.84 m |
| 30m | 10.125 | 46.2 ft / 14.09 m | 23.1 ft / 7.04 m | 23.1 ft / 7.04 m | 99.3 ft / 30.25 m |
| 20m | 14.175 | 33.0 ft / 10.06 m | 16.5 ft / 5.03 m | 16.5 ft / 5.03 m | 70.9 ft / 21.61 m |
| 17m | 18.118 | 25.8 ft / 7.87 m | 12.9 ft / 3.94 m | 12.9 ft / 3.94 m | 55.5 ft / 16.91 m |
| 15m | 21.225 | 22.0 ft / 6.72 m | 11.0 ft / 3.36 m | 11.0 ft / 3.36 m | 47.3 ft / 14.43 m |
| 12m | 24.94 | 18.8 ft / 5.72 m | 9.4 ft / 2.86 m | 9.4 ft / 2.86 m | 40.3 ft / 12.28 m |
| 10m | 28.4 | 16.5 ft / 5.02 m | 8.2 ft / 2.51 m | 8.2 ft / 2.51 m | 35.4 ft / 10.79 m |
| 6m | 50.125 | 9.3 ft / 2.85 m | 4.7 ft / 1.42 m | 4.7 ft / 1.42 m | 20.0 ft / 6.11 m |
More on building them: antenna & feedline guides.
Frequently asked questions
Why does the dipole formula use 468 instead of 492?
A half wavelength in free space is 492 ÷ f(MHz) feet. A real wire antenna resonates about 5% shorter because of end effects and the wire's thickness, so 492 × 0.95 ≈ 468 is used as the practical starting point.
Should I cut my dipole to the exact calculated length?
No. Cut it a little long, raise it to its working height, check where SWR is lowest and trim both legs equally. Shortening the wire moves the resonant frequency up.
Does an inverted-V need a different length?
Usually it ends up slightly longer than a flat dipole for the same frequency because the drooping legs and the ends' proximity to ground lower resonance. Start from the dipole length and trim on site.