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Antenna Length Calculator

Calculate antenna lengths from frequency: half-wave dipole, quarter-wave ground plane, 5/8-λ and full-wave loop

Typically 0.95 for wire antennas; thicker elements or end capacitance shorten further.

Wavelength λFree-space wavelength
2,068 m
λ/2 dipole (total length)λ/2 · 0.95
98,2 cm
Dipole leg (each side)λ/4 · 0.95
49,1 cm
λ/4 ground plane: radiatorλ/4 · 0.95
49,1 cm
λ/4 ground plane: radials≈ 4% longer than the radiator
51,1 cm
5/8-λ radiator5/8 λ · 0.95
1,228 m
Full-wave loop (circumference)1.02 × λ (loop correction)
2,109 m

Notes

These are starting lengths for construction – always fine-tune with an SWR meter or antenna analyzer (cut slightly long, then trim).

Surroundings, mounting height and the feed line noticeably affect resonance.

Accurate Antenna Length Calculations

The Antenna Length Calculator provides precise dimensions for various antenna types based on your target operating frequency. By inputting the frequency in MHz and a velocity factor, the tool calculates lengths for half-wave dipoles, quarter-wave ground planes including radials, 5/8-lambda radiators, and full-wave loops. These calculations account for practical construction factors like wire thickness and capacitance, providing reliable starting points for building efficient radio equipment tailored to your specific frequency requirements.

Construction Tips and Fine-Tuning

While the tool provides accurate theoretical lengths, real-world environmental factors such as mounting height, nearby obstacles, and feed line characteristics can significantly affect resonance. These results should be treated as starting points for construction. We recommend cutting antenna elements slightly longer than calculated and then performing fine-tuning with an SWR meter or antenna analyzer. This iterative trimming process ensures that your antenna achieves optimal performance despite the influence of local surroundings.

Frequently asked questions

What is the velocity factor?

The velocity factor accounts for how fast electromagnetic waves travel through specific materials like copper wire or aluminum tubing. A standard value of 0.95 is typical for most wire antennas. Thicker elements or added capacitance will lower this factor, resulting in shorter physical dimensions for your antenna components.

How do I fine-tune my antenna?

Because environmental factors like nearby buildings and feed lines affect resonance, you should use the tool's results as a starting point. Cut your antenna elements slightly longer than calculated and then trim them incrementally while monitoring with an SWR meter to reach the perfect match for your specific location.

What is a quarter-wave ground plane?

A quarter-wave ground plane consists of a radiator that is one-quarter of a wavelength long. It is typically used in combination with radials, which are slightly longer than the radiator to create an effective ground system for various radio frequency applications.

How is my data handled?

The Antenna Length Calculator processes all calculations locally within your web browser. No personal information or technical parameters are sent to a server or stored externally. Your calculation results remain on your device, ensuring privacy and speed while you plan your antenna construction.