Antenna Length Calculator
Calculate antenna length from operating frequency for quarter-wave, half-wave, full-wave and dipole antennas. Get instant measurements in meters, centimeters, feet and inches.
Enter Frequency Details
Recommended Antenna Length
Your Antenna Length Appears Here
Enter an operating frequency, choose the antenna type and click calculate to see the wavelength and antenna dimensions.
What Is an Antenna Length Calculator?
An antenna length calculator converts an operating frequency into the wavelength needed to estimate the physical length of an antenna. Since radio frequency and wavelength are directly related, knowing the frequency allows the theoretical wavelength to be calculated.
This calculator supports quarter-wave, half-wave, full-wave and half-wave dipole antenna calculations. Results are provided in meters, centimeters, feet and inches for easier construction and comparison.
How to Use the Antenna Length Calculator
Enter Frequency
Enter your desired operating or center frequency and select Hz, kHz, MHz or GHz.
Choose Antenna Type
Select quarter-wave, half-wave, full-wave or a half-wave dipole.
Calculate Length
Apply the velocity factor and calculate the recommended physical antenna length.
Antenna Length Formula
Radio waves travel through free space at approximately the speed of light. The full wavelength is calculated by dividing the speed of light by frequency.
λ = c ÷ f
In this formula, λ is wavelength in meters, c is approximately 299,792,458 meters per second, and f is frequency in hertz.
Quarter-Wave Antenna Formula
Length = (c ÷ f) × 0.25 × Velocity Factor
Half-Wave Antenna Formula
Length = (c ÷ f) × 0.5 × Velocity Factor
Half-Wave Dipole Antenna Length
A traditional dipole consists of two conductive elements extending in opposite directions from the feed point. The total tip-to-tip length is approximately one-half wavelength after applying the appropriate shortening or velocity factor.
Each side of a symmetrical half-wave dipole is approximately one-quarter wavelength long. The calculator therefore displays both the total dipole length and the length of each individual leg.
Each Side = Total Dipole Length ÷ 2
Common Frequency and Antenna Length Examples
The values below show approximate theoretical free-space dimensions before practical tuning or shortening factors are considered.
| Frequency | Full Wavelength | Half-Wave | Quarter-Wave |
|---|---|---|---|
| 27 MHz | 11.10 m | 5.55 m | 2.78 m |
| 50 MHz | 6.00 m | 3.00 m | 1.50 m |
| 100 MHz | 3.00 m | 1.50 m | 0.75 m |
| 144 MHz | 2.08 m | 1.04 m | 0.52 m |
| 433 MHz | 0.69 m | 0.35 m | 0.17 m |
| 915 MHz | 0.33 m | 0.16 m | 0.082 m |
| 2.4 GHz | 0.125 m | 0.062 m | 0.031 m |
Why Actual Antenna Length Can Differ
The theoretical wavelength is an excellent starting point, but a physical antenna does not always resonate at exactly the calculated free-space dimension. Conductor thickness, insulation, end effects and antenna geometry can change the required physical length.
Mounting height and nearby metal, buildings, vehicles, wiring and other conductive objects can also affect resonance. For practical antenna construction, it is common to begin slightly longer and carefully tune the antenna using appropriate RF measurement equipment.
Antenna Length Calculator FAQs
Divide the speed of light by the frequency to calculate the full wavelength. Multiply that wavelength by 0.25 for a quarter-wave antenna or 0.5 for a half-wave antenna.
A quarter-wave antenna has an electrical length of approximately one-quarter of the wavelength corresponding to its operating frequency.
A half-wave dipole has two approximately equal elements. Each side is approximately one-quarter wavelength before practical shortening and tuning are considered.
Velocity factor represents how the effective propagation characteristics of an antenna or transmission medium differ from the ideal free-space speed of light. It can be used as a practical adjustment to theoretical length.
Real-world materials, mounting conditions and nearby objects can shift antenna resonance. Calculated dimensions are therefore normally treated as a starting point for final tuning.
Yes. This calculator supports hertz, kilohertz, megahertz and gigahertz and automatically converts the entered frequency to hertz before calculating wavelength.