Convert between frequency and wavelength using the speed of light.
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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.
Assumptions and limitations
This converter assumes an electromagnetic wave travelling in a vacuum, using the fixed speed of light. In other media, such as glass or water, waves travel more slowly and the wavelength shifts, so results there are only approximate. It does not apply to sound, which travels at a completely different speed.
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.
Why is the speed of light treated as fixed here?
In a vacuum the speed of light is a defined constant, 299,792,458 metres per second, and air is close enough that the difference rarely matters. Because frequency and wavelength are linked through this constant, fixing it lets the tool convert exactly between the two for electromagnetic waves.