Dipole Antenna Length Calculator
Enter your target frequency to estimate the total dipole length and each leg length. This tool uses the common half-wave dipole formula and lets you apply a velocity factor for insulated wire or other real-world conductors.
Then: Each Leg = Total Length / 2
What this dipole length calculator does
A dipole antenna is one of the most practical and beginner-friendly antennas for HF and shortwave work. This calculator helps you quickly estimate the physical wire length needed for a half-wave dipole at your chosen operating frequency.
Instead of guessing and repeatedly re-cutting wire, you can start with a solid baseline. The output gives you both total tip-to-tip length and the length of each leg from center feedpoint to end insulator.
The core dipole formula
Standard equation
The most common field formula for a half-wave dipole is:
- Total length (feet) = 468 / f(MHz)
- Each leg (feet) = 234 / f(MHz)
This assumes near-ideal conditions. In practical installations, wire insulation, nearby objects, and antenna height can shift resonance slightly. That is why this calculator includes a velocity factor input.
Why velocity factor matters
Real conductors and insulation can make the antenna electrically longer than its physical length. A velocity factor below 1.00 compensates for that by shortening your starting cut length. In many real builds, a VF between 0.95 and 0.98 is a good starting point.
How to use the calculator
- Enter your desired operating frequency.
- Select the frequency unit (Hz, kHz, MHz, or GHz).
- Choose a material preset or enter a custom velocity factor.
- Click Calculate Length to view total and per-leg dimensions in feet, meters, and inches.
For best results, cut your antenna a little long and trim equally on both legs during tuning.
Quick reference values (VF = 1.00)
| Band / Frequency | Total Length (ft) | Each Leg (ft) | Total Length (m) |
|---|---|---|---|
| 80m (3.5 MHz) | 133.7 | 66.9 | 40.8 |
| 40m (7.1 MHz) | 65.9 | 33.0 | 20.1 |
| 20m (14.2 MHz) | 33.0 | 16.5 | 10.0 |
| 10m (28.4 MHz) | 16.5 | 8.2 | 5.0 |
Real-world tuning tips
1) Height above ground affects resonance
A lower antenna typically resonates slightly lower in frequency than expected. If installed close to ground, you may need to trim a little more than predicted.
2) Keep both legs equal
When tuning, always trim both legs by the same amount. Unequal trimming can skew current distribution and degrade pattern symmetry.
3) Use a current balun at the feedpoint
A 1:1 current balun (or choke) helps reduce feedline radiation and improves consistency in SWR readings during tuning.
4) Tune in final installation position
Measurements on the ground are useful for rough checks, but final resonance should be adjusted with the antenna mounted at its intended operating height and orientation.
Safety checklist
- Never install antennas near overhead power lines.
- Use proper strain relief and weather-safe supports.
- Ground and protect your station for lightning safety.
- Follow local regulations and band plans for operation.
Bottom line
This dipole length calculator gives you a practical starting point for fast antenna construction. Use the computed values, install carefully, and finalize with on-air or analyzer-based trimming. A simple dipole, correctly cut and tuned, remains one of the most reliable antennas for everyday operation.