Dipole Antenna Length Calculator
Enter the frequency and the shortening factor.
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Dipole Antenna Length Calculator by TheCalcTools
How the Dipole Antenna Length Calculator works
A half-wave dipole is about half a wavelength long: λ = c ÷ f, so λ/2 = 149.9 ÷ f(MHz) metres. End effects and wire thickness make the resonant length a few percent shorter, which the factor accounts for (the classic 468 ÷ f feet uses 0.95).
Cut slightly long and trim while checking SWR, since height above ground and nearby objects also shift resonance.
The formula
Worked example
Using the default values shown in the calculator:
| Frequency (MHz) | 14.2 |
|---|---|
| Shortening factor | 0.95 |
- At 14.2 MHz a half-wave dipole is 10.028 m (32.90 ft), 5.014 m per leg.
Result:
| Half-wave dipole length (m) | 10.028 |
|---|---|
| Each leg (m) | 5.014 |
| Half-wave length (ft) | 32.90 |
| Quarter-wave vertical (m) | 5.014 |
| Free-space wavelength (m) | 21.112 |
Frequently asked questions
How long is a 20 m band dipole?
At 14.2 MHz, about 10.0 m (33 ft) in total, two legs of about 5 m.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.