Frequency-Wavelength Converter
ScienceConvert electromagnetic wave frequency to wavelength and back using the speed of light — for radio, light, and RF engineering. Hz, kHz, MHz, GHz, nm, m.
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What is a Frequency ↔ Wavelength?
The Frequency-Wavelength Converter converts between electromagnetic wave frequency (Hz through THz) and wavelength (nanometres through kilometres) using the speed of light relationship f = c/λ. Unlike converting between two frequency units or two length units, this is a cross-quantity conversion — frequency and wavelength describe the same wave from two different, inversely related perspectives.
Enter a value in either a frequency or wavelength unit and the converter calculates the equivalent in your chosen target unit instantly. For frequency-only unit conversions, see the Frequency Converter.
How to use this Frequency ↔ Wavelength calculator
- Choose your starting unit from the source dropdown — for example, "Megahertz (MHz)" for a frequency, or "Nanometres (nm)" for a wavelength.
- Enter the numeric value you want to convert in the input field.
- Choose your target unit from the destination dropdown — for example, "Metres (m)" for the resulting wavelength.
- Read the converted result, which updates instantly as you type or change units.
- Use the swap (⇅) button if you need to reverse the conversion direction.
- Use the copy button to grab the result for an antenna design calculation or physics problem.
Formula & Methodology
Frequency units convert to Hz linearly. Wavelength converts to and from frequency using: Frequency (Hz) = Speed of Light (299,792,458 m/s) ÷ Wavelength (m) Wavelength (m) = Speed of Light (299,792,458 m/s) ÷ Frequency (Hz) Worked example — converting a 100 MHz FM radio frequency to wavelength in metres: Wavelength = 299,792,458 ÷ 100,000,000 = 2.998 metres This matches the commonly cited approximately-3-metre wavelength for FM radio broadcast frequencies, a useful reference for antenna length calculations.
Frequently Asked Questions
Divide the speed of light (299,792,458 m/s) by the frequency in Hz to get wavelength in metres — for example, a 100 MHz radio signal has a wavelength of about 3 metres. Enter your value with a frequency unit as the source and a length unit as the target and the converter applies this automatically.
Frequency and wavelength are inversely related — as frequency increases, wavelength decreases proportionally, since both describe the same wave but from different angles (how many cycles per second versus how long each cycle spans in space). This reciprocal relationship (f = c/λ) is why the conversion isn't a fixed multiplier the way most unit conversions are.
Visible light spans roughly 380 to 700 nanometres in wavelength, corresponding to frequencies of about 430 to 790 terahertz — violet light has the shortest wavelength and highest frequency in this range, while red light has the longest wavelength and lowest frequency.
A 2.4 GHz WiFi signal has a wavelength of about 12.5 cm, and a 5 GHz signal has a wavelength of about 6 cm — enter either frequency with 'Gigahertz (GHz)' as the source and a length unit like 'Centimetres (cm)' as the target to see this calculated directly.
No — this converter uses the speed of light, which only applies to electromagnetic waves (radio, microwave, light, X-rays). Sound waves travel at a much slower, medium-dependent speed (about 343 m/s in air), so converting sound frequency to wavelength requires a different speed constant. See the [Sound Converter](/sound-converter/) for sound-specific unit conversions.
Antenna dimensions are typically designed as a fraction of the target frequency's wavelength (like a quarter-wave or half-wave antenna), so accurately converting a radio frequency to its wavelength is a necessary first step in antenna design and RF engineering.
The full electromagnetic spectrum — radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays — is organised by frequency and wavelength, with radio waves having the lowest frequency and longest wavelength, and gamma rays having the highest frequency and shortest wavelength.
Yes — the speed of light in vacuum (299,792,458 m/s) is defined as an exact value by the International System of Units, making frequency-to-wavelength conversions in vacuum mathematically precise rather than approximate.
Light slows down when passing through a medium like water or glass, which shortens its wavelength while its frequency stays constant — this converter calculates the vacuum (or air, approximately the same) relationship, so results for light travelling through a dense medium would need an additional refractive index adjustment.
Yes — the same f = c/λ relationship applies across the entire electromagnetic spectrum, though X-ray and gamma-ray wavelengths are typically expressed in picometres or smaller units not currently included in this converter's unit list; nanometres is the smallest wavelength unit offered here.
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