Antenna Length Calculator
Quarter-wave, half-wave and full-wave lengths for a frequency, with the dipole half-length.
Results
Antenna length
49.104
cm
Wavelength
2.06753
m
Antenna length
98.208
cm
Antenna length
196.42
cm
Antenna length
92.315
cm
What this tool does
Radio waves travel slightly slower along a wire than through free space, so a resonant element is always a little shorter than the pure arithmetic suggests. The velocity factor covers that: around 0.95 for a thin bare wire, lower for thick or insulated elements. Trim long and cut down — an antenna cut short cannot be uncut.
Formula
λ = c ÷ f ; quarter wave = λ ÷ 4 × speed factor
Variables
| Symbol | Meaning | Unit |
|---|---|---|
fq | Frequency | MHz |
vf | Velocity factor | — |
Q4 | Antenna length | cm |
WL | Wavelength | m |
H2 | Antenna length | cm |
FW | Antenna length | cm |
DI | Antenna length | cm |
Worked example
- Frequency145 MHz
- Velocity factor0.95
- Antenna length49.104 cm
- Wavelength2.06753 m
- Antenna length98.208 cm
- Antenna length196.42 cm
- Antenna length92.315 cm
Limitations
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.