Convert between frequency and wavelength using the speed of light.
Calculated instantly in your browser.
How do you convert frequency to wavelength?
Wavelength λ = c ⁄ f and frequency f = c ⁄ λ, where c = 299,792,458 m/s is the speed of light; the period is T = 1 ⁄ f. Frequency and wavelength are inversely proportional. For example, a 100 MHz FM signal has a wavelength of 299,792,458 ⁄ 100,000,000 ≈ 3 metres. This applies to electromagnetic waves in a vacuum (and nearly in air).
Understanding your result
Frequency and wavelength are inversely proportional: as one rises, the other falls, with the speed of light as the constant of proportionality. This applies to electromagnetic waves travelling in a vacuum (and very nearly in air).
Formula and method
Wavelength λ = c ⁄ f and frequency f = c ⁄ λ, where c = 299,792,458 m/s is the speed of light. The period is T = 1 ⁄ f.
Worked example
A 100 MHz FM signal has a wavelength of 299,792,458 ⁄ 100,000,000 ≈ 3 metres.
How to use this tool
- Choose frequency → wavelength or the reverse.
- Enter the value and its unit.
- Read the converted result and period.
Common mistakes to avoid
- Mixing up the unit prefixes (MHz vs GHz).
- Using the speed of light for sound waves — sound is far slower.
About the Frequency & Wavelength Converter
This converter switches between the frequency and wavelength of an electromagnetic wave using the speed of light. Enter a frequency to get its wavelength, or a wavelength to get its frequency, along with the period.
Who should use this tool
Radio and RF engineers, students, ham-radio operators and antenna builders.
Benefits
- Both directions in one tool.
- Picks readable units automatically.
- Also shows the wave period.
- Uses the exact speed of light.
Practical use cases
- Finding the wavelength of a Wi-Fi or radio band.
- Sizing an antenna for a frequency.
- Checking physics homework on waves.
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Frequently asked questions
What speed does this use?
The speed of light in a vacuum, c = 299,792,458 m/s, which is accurate for radio and light in air. Inside other media, waves travel slower.
Does this work for sound?
No — sound travels around 343 m/s in air, not the speed of light, so the wavelengths would be completely different.