Radio Band Wavelength Calculator
Pick a radio band — FM, AM, Wi-Fi, CB, LTE — or enter any frequency to get its wavelength, half-wave and quarter-wave lengths.
How it works
λ (m) = c ÷ f = 300 ÷ f(MHz) · ½λ = λ ÷ 2 · ¼λ = λ ÷ 4
Wavelength is the distance one full cycle of a wave travels, and it is inversely proportional to frequency: the higher the band, the shorter the wave. Because radio waves move at the speed of light (~3×10⁸ m/s), a handy shortcut is 300 divided by the frequency in MHz to get metres. Knowing the wavelength immediately tells you how big a resonant antenna needs to be.
Worked example
Wi-Fi at 2450 MHz gives λ = 300 ÷ 2450 = 0.1224 m, or 12.24 cm. A quarter-wave antenna for it is 0.1224 ÷ 4 = 3.06 cm — which is why 2.4 GHz whip antennas are tiny.
Frequently asked questions
Why does higher frequency mean shorter wavelength?
Wavelength equals wave speed divided by frequency. Since all radio waves travel at the same speed (the speed of light), doubling the frequency halves the wavelength. That is why microwave antennas are far smaller than AM broadcast antennas.
Is the physical antenna exactly a quarter wavelength?
Almost — a real element is cut about 5% shorter than the theoretical quarter wave to account for the wire velocity factor and end effect. Use the antenna length calculator to apply that correction.
What wavelength is Wi-Fi?
The 2.4 GHz band is about 12.2 cm and the 5 GHz band about 5.5 cm. The shorter 5 GHz wave carries more data but is absorbed more by walls, giving it less range.
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This calculator is for educational purposes. Double-check important results before acting on them.