Quarter wave
Often the first number to check for a simple vertical radiator.
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Wavelength Calculator
Convert frequency to wavelength and common antenna lengths for ham radio bands.
Convert frequency to wavelength
Get an instant quarter-wave, dipole cut length, and practical antenna starting points for the band you want to use.
Live wavelength results
14.074 MHz
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Total length
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Per leg
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Full wavelength
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Half wave
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5/8 wave
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Velocity factor 0.950
Adjusted cut lengths
Use these numbers when you want a practical starting point for insulated wire, matching sections, or stub work.
How to use these numbers
Why calculated lengths are only a starting point
The free-space number is where the planning starts, not where the final trim ends. Real antennas are affected by conductor diameter, insulation, mounting height, nearby metal, soil conditions, end effects, and matching hardware. Even a simple wire antenna can shift enough that the first cut should be treated as an informed estimate rather than a promise.
Calculate first, cut a little long, install, and trim after measurement. If you already know the antenna family, move into Antenna Designer or a specific tool such as Ground Plane Antenna Calculator.
Worked example: 14.074 MHz
14.074 MHz is a common FT8 operating frequency on 20 meters. At that frequency, the quarter-wave starting length is about 5.33 meters / 17.47 feet. A simple center-fed dipole works out to roughly 10.65 meters / 34.95 feet total, or two legs of about 5.33 meters / 17.47 feet each before final trimming.
From there, the usual next steps are to open Antenna Designer, check the feedline with Coax Loss Calculator, and choose a layout in Wire Deployments before final trimming.
Velocity factor explained simply
Velocity factor is just a way to account for RF traveling more slowly in real materials than it does in free space. If you are calculating a matching section, a coax stub, or insulated wire, the adjusted number is often more useful than the ideal free-space value. That is why this page lets you add velocity factor directly instead of treating it as a separate step.
For a bare-wire antenna in open space, you may start with the free-space value and trim later. For coax, stubs, phasing lines, or insulated wire, velocity factor matters much sooner. The simple version is: if the material changes how RF travels, the physical length changes too.
When to use this calculator vs Antenna Designer
Use this page when the first question is pure math: “What is the wavelength at this frequency?” or “What is the quarter-wave or half-wave starting point?” That makes it the right tool when you are roughing out a band change, checking whether an antenna idea fits available space, or comparing one operating frequency against another.
Use Antenna Designer when the next question is design-specific: dipole versus EFHW, vertical versus Yagi, feed style, or the actual build path. If you already know the project is a vertical, jump directly into Ground Plane Antenna Calculator. After the dimensions look sensible, compare feedline impact in Coax Loss Calculator.
Quick ham band reference
These are rounded free-space starting points for common amateur bands. Use them for rough planning, then calculate the exact operating frequency above when the build or matching section depends on tighter numbers.
| Band | Example Frequency | Approx. Wavelength | Approx. Quarter-Wave |
|---|---|---|---|
| 80m | 3.75 MHz | 79.95 m | 19.99 m |
| 40m | 7.15 MHz | 41.93 m | 10.48 m |
| 20m | 14.175 MHz | 21.15 m | 5.29 m |
| 10m | 28.85 MHz | 10.39 m | 2.60 m |
| 2m | 146 MHz | 2.05 m | 0.51 m |
| 70cm | 446 MHz | 0.67 m | 0.17 m |
If the next question is whether that band is likely usable today, check Full Propagation View. If the question is where a mode normally operates inside the band, compare against band plan references or Band Privileges Lookup before you transmit.
Wavelength calculator FAQ
The calculated number is a starting point, not the final cut. Real antennas are affected by insulation, element diameter, mounting height, nearby objects, matching hardware, and end effects. Use the result to get close, then trim and test.
Velocity factor matters whenever the material or structure slows RF relative to free space. It is especially useful for insulated wire, matching sections, phasing lines, and stubs. For a bare-wire antenna in open space it may matter less, but it still gives you a practical adjustment when the build is not ideal free space.
Use this page when you need fast frequency-to-wavelength math and basic antenna fractions. Use Antenna Designer or a dedicated calculator such as Ground Plane Antenna Calculator when the next question is a specific antenna type rather than raw wavelength.