Wavelength to frequency calculator (light)
Pick the wavelength unit and enter its value to get the wave frequency in vacuum. Useful for physics students and anyone working with lasers, fiber or radio.
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How to use it
- Enter wavelength and unit.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
f = c / λ, where c = 299792458 m/s is the defined speed of light in vacuum and λ is the wavelength in meters.
Example
Inputs: Wavelength = 500, Unit = nanometers (nm). Result: Frequency: 599,584,916,000,000 Hz; Frequency in THz: 599.584916 THz; Frequency in GHz: 599,584.916 GHz.
Limits and caveats
- The result is for the wave in vacuum. Inside glass or water the frequency is the same but the wavelength shrinks by the refractive index.
Questions about this tool
What is the frequency of green light?
Light with a 530 nm wavelength has a frequency of about 566 THz.
Does frequency change when light enters water?
No. The frequency stays the same; the speed and wavelength change.
Why is the speed of light an exact number?
Since 1983 the meter has been defined from the speed of light, so it is exactly 299792458 m/s.