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How to use
Use the wavelength-to-frequency calculator to convert wavelength to frequency, frequency to wavelength, or solve propagation speed from v=fλ. The same relationship works for different waves when the correct speed for the medium is used. For 500 nm light in vacuum, first convert 500 nm to 5×10⁻⁷ m. Then f = 299,792,458 ÷ (5×10⁻⁷) = 5.99584916×10¹⁴ Hz, or 599.584916 THz. A sound wave of wavelength 0.5 m at an entered speed of 340 m/s instead has frequency 680 Hz; use the speed of the intended medium.
- Choose the variable to solve for.
- Enter the other two values and units.
- For light in vacuum you can use 299,792,458 m/s as propagation speed.
How it is calculated
Example
Example: a 100 MHz radio wave in vacuum has wavelength about 2.9979 m.
Important notes
Sound speed is not universal, and light travels slower in materials than in vacuum. Use a propagation speed appropriate to the medium.
Worked examples and interpreting results
Wavelength is wave speed divided by frequency. For light in vacuum, use 299,792,458 m/s; for another medium, enter the appropriate propagation speed.
| Case | Calculation | Result |
|---|---|---|
| 100 MHz in vacuum | 299792458 ÷ 100000000 | 2.997925 m |
| 200 MHz in vacuum | 299792458 ÷ 200000000 | 1.498962 m |
How to check the result
At a fixed wave speed, doubling frequency halves wavelength. Convert MHz to Hz by multiplying by one million, and do not use light speed for a sound wave.
Wavelength to frequency: MHz, nm and wave speed
Frequency equals wave propagation speed divided by wavelength. For light in vacuum use 299,792,458 m/s; when using sound or another medium, enter its appropriate speed. Convert nanometres and megahertz to SI units first.
- Wavelength of a 100 MHz vacuum radio wave: 299792458 ÷ 100000000 = ≈ 2.9979 m
- Frequency of 600 nm light in vacuum: 299792458 ÷ 0.0000006 = ≈ 499.65 THz
- Sound at 340 m/s, wavelength 0.5 m: 340 ÷ 0.5 = 680 Hz
Important distinction
The speed depends on the propagation medium. A wavelength in nanometres must be converted to metres, and a radio frequency in MHz must be multiplied by one million to get hertz.
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Frequently asked questions
How do I convert wavelength to frequency?
Use f = v/λ. Enter the wavelength and the wave speed in compatible units; for light in vacuum you can use 299,792,458 m/s.
Is this only a frequency converter?
No. It solves v, f or λ from the other two variables.
Is 299,792,458 m/s exact?
Yes. It is the defined exact SI value for the speed of light in vacuum.
How does increasing frequency affect wavelength?
At constant propagation speed, wavelength is inversely proportional to frequency: doubling frequency halves wavelength. Convert speed and frequency to compatible units before applying the relation.
How do I convert nm to Hz?
Multiply nanometres by 10⁻⁹ to obtain metres, then divide propagation speed in m/s by wavelength in metres. The conversion depends on the wave speed in the medium.
How do I convert wavelength in metres to frequency in hertz?
Use frequency f = wave speed v ÷ wavelength λ, using v in metres per second and λ in metres. For a wave travelling at 300 m/s with wavelength 2 m, f = 150 Hz. For light in a vacuum use the defined speed 299,792,458 m/s.
Can I use the speed of light to convert sound wavelength to frequency?
No. Use the wave speed in the relevant medium. Light in vacuum travels at 299,792,458 m/s, whereas sound travels at a much lower speed that depends on the medium and conditions. At fixed speed, wavelength and frequency are inversely related.