This tool converts from Wavelength in nm, um, mm, cm, m, inches or feet to Frequency in Hz, kHz, MHz, GHz.
Frequency f is given by the formula
f = c/λ
where, c is the speed of light and λ is the wavelength. As the wavelength increases the frequency decreases.
In a vacuum, the speed of light is c = 299,792,458 meters/second. It is slower in other media such as in glass for instance where the speed is 200,000,000 meters/second. Change the value of c in the calculator above to calculate the frequency in this case.
For a fixed value of wavelength, as c increases, so does f.
The picture below shows the wavelength (λ) of a sine wave
Frequency and Wavelength in RF Engineering
Most Radio engineers are used to referring to regions of the electromagnetic spectrum in terms frequency – for instance the Wi-Fi band is 2.4 GHz and 5 GHz.
The exception is when you get to lower frequencies in HF and VHF. At these bands, hobbyists and technologists refer to wavelength. For instance the 2 meter and 70 cm bands. It can be a little confusing sometimes.
This calculator clears up that confusion to make the conversion between wavelength and frequency easy.