Wavelength Calculator
Converts frequency to wavelength and back, with half and quarter wavelengths given as well since those are what antenna and stub lengths are built from.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
λ = v ÷ f v = c × velocity factor
Wavelength is how far the wave travels in one cycle, so it is speed divided by frequency. In a vacuum that speed is c. In coax or any dielectric it is slower — which is why a cable cut to a quarter wavelength is physically shorter than the free-space figure suggests.
What to watch out for
The shortcut worth memorising: wavelength in metres ≈ 300 ÷ frequency in MHz. It is accurate to within a fraction of a percent, since the speed of light is 299.79 rather than 300 million metres per second.
The velocity factor matters whenever the wave is inside something. Radio in free space travels at c; the same signal in RG-58 coax travels at about 0.66c, so a quarter-wave stub in that cable is a third shorter than the free-space quarter wavelength.
Frequently Asked Questions
How do I convert frequency to wavelength?
Divide the speed of light by the frequency. For a quick answer in metres, divide 300 by the frequency in MHz — 100 MHz gives about 3 m.
What is velocity factor?
The fraction of the speed of light at which a wave travels through a given medium. Free space is 1.0, solid polyethylene coax about 0.66, foam dielectric around 0.82. It shortens every physical length derived from wavelength.
What is the wavelength of Wi-Fi?
About 12.5 cm at 2.4 GHz and roughly 6 cm at 5 GHz. That is why the antennas are small, and why a quarter-wave element at 2.4 GHz is only about 3 cm long.