Why does the formula use 468 instead of 492?

The theoretical half-wavelength in free space is 492 / f(MHz) feet. The factor 468 applies a velocity factor of ~0.95 to account for the fact that current travels slightly slower along a real wire than in free space, improving resonance accuracy for bare copper wire in open air.

What is velocity factor and when should I change it?

Velocity factor (VF) is the ratio of signal speed in a medium vs. free space. Bare copper wire in open air is typically 0.95–0.97. Insulated wire or elements near ground may be 0.90–0.95. Lower the VF slider if your antenna is covered in insulation or if testing shows resonance lower than expected.

Does this work for VHF and UHF frequencies?

Yes. The same formula applies at any frequency. At VHF (144 MHz) the total length is roughly 1 meter; at UHF (432 MHz) it is about 33 cm. Just enter the frequency in MHz and read the result.

What is the difference between total length and element length?

A dipole has two equal arms extending in opposite directions from the feed point. The total length is the end-to-end span of the antenna. Each element (arm) is half that — the length you need to cut for one wire.

Is this calculator accurate for all dipole types?

It gives a good starting point for a standard center-fed dipole. Folded dipoles, loaded dipoles, and cage dipoles may have different effective lengths. Use this as a baseline, then trim for minimum SWR with an antenna analyzer.

Dipole Antenna Calculator

Name: Dipole Antenna Calculator
Availability: InStock
Author: Nham Vu

Enter a frequency and instantly get the total and per-element length of a half-wave dipole antenna in meters and feet.

Antenna Parameters

Operating Frequency (MHz)

Enter any frequency from 0.1 MHz to 30 000 MHz

Velocity Factor: 0.95

0.80 (insulated) 1.00 (free space)

Display Units

Results

Enter a frequency and click Calculate

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Summary

Enter a frequency and instantly get the total and per-element length of a half-wave dipole antenna in meters and feet.

How it works

Enter your desired operating frequency in MHz (e.g., 14.225 for 20 m band).
Select whether you want results in meters, feet, or both.
The calculator applies the half-wave formula: total length = 468 / f(MHz) feet.
Each dipole arm (element) is exactly half the total length.
Copy or note the values and cut your antenna wire accordingly.
An optional velocity factor lets you adjust for insulated or shortened dipoles.

Use cases

Cut wire for a DIY HF ham radio dipole antenna.
Verify the resonant length of an existing antenna at a given frequency.
Plan a multi-band fan dipole by calculating each leg separately.
Estimate antenna dimensions for a VHF or UHF dipole.
Cross-check commercial antenna specifications.
Quickly determine element length for a balanced feed dipole.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu