Wavelength from Frequency Calculator
Every electromagnetic wave has a wavelength tied to its frequency by a single constant, the speed of light. This calculator takes a frequency in megahertz and returns the wavelength in meters using the relationship that wavelength equals the speed of light divided by frequency. The speed of light in a vacuum is a defined constant of exactly 299,792,458 meters per second, fixed by the international system of units that the National Institute of Standards and Technology maintains for the United States. Because the constant is exact, the wavelength you get is determined entirely by the frequency you enter, with no measurement uncertainty in the relationship itself. Radio engineers, antenna builders, optics students and anyone working with waves use this conversion constantly: it sets antenna dimensions, waveguide sizes and the spacing of diffraction effects. Enter your frequency and read off the wavelength directly. Note that inside a material the wave travels slower than in a vacuum, so the in-material wavelength is shorter by the velocity factor; this calculator gives the free-space figure. Every result here is computed deterministically from the formula shown below, with a worked example that reconciles exactly to the calculator so you can follow each step yourself.
Wavelength equals the speed of light divided by frequency: lambda = c / f. At 100 MHz the wavelength is 2.9979 m, using c = 299,792,458 m/s.
Wavelength from Frequency formula
lambda = c / f
lambda = wavelength in meters
c = 299,792,458 m/s (speed of light, exact)
f = frequency in hertz (MHz x 1,000,000)
The speed of light is a defined constant, so the wavelength depends only on the frequency. Multiply megahertz by one million to convert to hertz before dividing.
Worked example
Find the wavelength of an FM broadcast signal at 100 megahertz.
- Convert: f = 100 MHz = 100,000,000 Hz
- lambda = 299,792,458 / 100,000,000
- lambda = 2.9979 meters
The wavelength is 2.9979 meters. This is the calculator's default input, so the result above matches the widget exactly.
Wavelength at common frequencies
Free-space wavelength using lambda = c / f.
| Frequency (MHz) | Wavelength (m) |
|---|---|
| 1 | 299.7925 |
| 10 | 29.9792 |
| 100 | 2.9979 |
| 1,000 | 0.2998 |
| 2,400 | 0.1249 |
Speed of light and SI units: US National Institute of Standards and Technology (NIST).
Wavelength from Frequency Calculator: frequently asked questions
What is wavelength?
Wavelength is the distance between two corresponding points on consecutive cycles of a wave, such as crest to crest. For electromagnetic waves it is set by the frequency and the speed of light, so a higher frequency means a shorter wavelength. It is usually measured in meters, centimeters or nanometers depending on the band.
What value of the speed of light does this use?
It uses the exact defined value of 299,792,458 meters per second in a vacuum. Since 1983 the meter has been defined in terms of the speed of light, so this constant is exact by definition rather than measured, a convention maintained for the United States by the National Institute of Standards and Technology.
Is the wavelength different inside a cable or material?
Yes. Inside a medium the wave travels slower than in a vacuum by the velocity factor of that medium, so the wavelength shrinks by the same factor. A coaxial cable with a velocity factor of 0.66, for example, carries a wave with a wavelength about 66 percent of the free-space figure. This calculator reports the free-space wavelength.
How do I convert megahertz to hertz?
Multiply by one million. One megahertz equals 1,000,000 hertz, and one gigahertz equals 1,000,000,000 hertz. The calculator does this conversion internally before dividing the speed of light by the frequency.
What is the wavelength formula?
Wavelength equals the speed of light divided by frequency, lambda = c / f, with c equal to 299,792,458 meters per second and f in hertz. For 100 megahertz that is 299,792,458 divided by 100,000,000, about 2.9979 meters.
Official sources
- Measurement units, physical constants and computational reference data: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.