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Frequency-Wavelength Converter

Science

Convert electromagnetic wave frequency to wavelength and back using the speed of light — for radio, light, and RF engineering. Hz, kHz, MHz, GHz, nm, m.

Reviewed by the thecalcu.com team · Last updated July 25, 2026

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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.

Why Use a Frequency-Wavelength Converter?

RF engineers need to know a radio frequency's wavelength for antenna design, optics engineers work with light wavelengths that need translating to frequency for certain calculations, and students learning the electromagnetic spectrum need to move fluidly between the two representations. Because the relationship is a division by the speed of light rather than a fixed multiplier, this conversion is more error-prone to do by hand than a typical unit conversion.

Who Should Use This Converter?

  • RF and antenna engineers converting target frequencies into wavelengths for antenna dimension calculations.
  • Optics and photonics engineers working between light wavelength specifications and frequency-based calculations.
  • Physics and electrical engineering students learning the relationship between frequency and wavelength across the electromagnetic spectrum.
  • Wireless communication engineers converting between WiFi, cellular, and radio frequencies and their corresponding wavelengths.

What Insights Does the Frequency-Wavelength Converter Give You?

The main output is the converted value in your chosen target unit, calculated precisely using the exact speed of light constant. Because frequency and wavelength are inversely related, the converter also implicitly shows you the inverse relationship in action, a higher frequency always corresponds to a shorter wavelength, and vice versa.

How to use this Frequency ↔ Wavelength calculator

  1. Choose your starting unit from the source dropdown, for example, "Megahertz (MHz)" for a frequency, or "Nanometres (nm)" for a wavelength.
  2. Enter the numeric value you want to convert in the input field.
  3. Choose your target unit from the destination dropdown, for example, "Metres (m)" for the resulting wavelength.
  4. Read the converted result, which updates instantly as you type or change units.
  5. Use the swap (⇅) button if you need to reverse the conversion direction.
  6. Use the copy button to grab the result for an antenna design calculation or physics problem.
Show formula & methodology ↓Show less ↑

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.

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Frequently Asked Questions

How do I convert frequency to wavelength?
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.
Why is this conversion a division, not a simple multiplication?
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.
What is the wavelength of visible light?
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.
How do I convert a WiFi frequency to its wavelength?
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.
Does this formula work for sound waves as well as electromagnetic waves?
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.
Why do antenna designers need to know a radio wave's wavelength?
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.
What is the relationship between frequency, wavelength, and the electromagnetic spectrum?
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.
Is the speed of light used in this converter exact?
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.
How does wavelength change when light travels through a medium other than vacuum?
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.
Can I use this converter for X-ray or gamma-ray wavelengths?
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.
Also known as
frequency to wavelength converterhz to nm converterwavelength to frequency calculatorradio frequency to wavelength converterlight wavelength converter