This frequency to wavelength converter turns a frequency in hertz, kilohertz, megahertz or gigahertz into a wavelength, and works in reverse as a wavelength to frequency calculator. It uses λ = c ÷ f with the speed of light in vacuum, which is exactly 299,792,458 m/s by definition of the meter.
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How to use the frequency to wavelength converter
- Enter the frequency, for example 100 MHz for an FM station.
- Choose the frequency unit and the wavelength unit.
- Read the frequency to wavelength converter result: 100 MHz ≈ 2.998 m.
A quick MHz to meters rule: wavelength in meters ≈ 300 ÷ frequency in MHz. For wavelength to frequency, swap the two: f = c ÷ λ.
What is the frequency to wavelength formula?
- λ = c ÷ f (wavelength in meters, frequency in hertz)
- f = c ÷ λ for the reverse
- c = 299,792,458 m/s, the speed of light in vacuum. It has been an exact defined constant since the meter was redefined in 1983, and it is one of the defining constants of the SI.
Convert the frequency to hertz first: 1 kHz = 103 Hz, 1 MHz = 106 Hz, 1 GHz = 109 Hz, 1 THz = 1012 Hz.
Quick estimate for radio: wavelength in meters ≈ 300 ÷ frequency in MHz.
Frequency to wavelength converter worked examples
| Signal | Frequency | Wavelength |
|---|---|---|
| AM radio (low end of band) | 540 kHz | 555.2 m |
| FM radio | 100 MHz | 2.998 m |
| Wi-Fi / Bluetooth / microwave oven | 2.4 GHz | 12.49 cm |
| Wi-Fi 5 GHz band | 5 GHz | 6.00 cm |
| Green light | 545 THz | 550 nm |
Example: 2.4 GHz → 299,792,458 ÷ 2,400,000,000 = 0.1249 m = 12.49 cm. A quarter-wave antenna for this band is therefore about 3.1 cm long.
Assumptions and limits
The frequency to wavelength converter assumes electromagnetic waves in a vacuum. In air the difference is under 0.03%, but in glass, water or a coaxial cable the wave travels slower, so the wavelength is shorter by the material’s refractive index or velocity factor. Sound waves are different again: in air at about 20 °C sound travels near 343 m/s, so the frequency to wavelength converter does not apply to audio.
Wavelengths of common signals
From the power grid to visible light, the same formula applies; only the scale changes:
| Signal | Frequency | Wavelength in vacuum |
|---|---|---|
| US power grid | 60 Hz | 4,997 km |
| AM radio | 1 MHz | 299.8 m |
| FM radio | 100 MHz | 2.998 m |
| Wi-Fi | 2.4 GHz | 12.49 cm |
| Wi-Fi | 5 GHz | 6 cm |
| Millimeter-wave 5G | 28 GHz | 10.71 mm |
| Green light | 540 THz | 555.2 nm |
Light at 540 THz is the frequency used in the SI definition of the candela; its wavelength is about 555 nm, in the green.
Antenna length and velocity factor
A quarter-wave antenna is about λ ÷ 4 long, so a 146 MHz antenna is about 0.51 m. In a cable or other medium, waves travel slower than in vacuum, so the wavelength is shorter: λ = v × c ÷ f, where v is the velocity factor given on the cable datasheet. A cable with v = 0.66 carries a 100 MHz signal with a wavelength of about 1.98 m. Use the length converter to change meters to feet or inches.
Wavelength inside a cable
Waves travel slower in cable than in free space, so cut lengths must be scaled by the cable’s velocity factor. A quarter-wave stub for 146 MHz is about 51.3 cm in free space. In solid-polyethylene coax with a velocity factor of 0.66, the same electrical quarter wave is only about 33.9 cm. Foam-dielectric cables run around 0.78 to 0.85, so check the data sheet.
The frequency to wavelength converter gives the free-space value from λ = c ÷ f. Multiply by the velocity factor for cable, and trim a little long so you can tune the final length with an analyzer.
A microwave oven at 2.45 GHz has a free-space wavelength of about 12.2 cm, which is why the hot and cold spots in an oven without a turntable are a few centimeters apart: half a wavelength is about 6 cm. Wi-Fi at 2.4 GHz has nearly the same wavelength.
Related converters and calculators
Related tools:
- Length converter: m, ft, in
- Image resolution converter: dpi and ppi
- Electric field strength converter: V/m
- Voltage converter: V and mV
- Luminance converter: nits and fL
Sources
NIST CODATA: Speed of light in vacuum; BIPM: SI Brochure.
Questions about this calculator
What is the formula for frequency to wavelength?
λ = c ÷ f, with c = 299,792,458 m/s in vacuum.
How do I convert MHz to meters?
Divide 299.792458 by the frequency in MHz. For example, 50 MHz ≈ 6.00 m.
What is the wavelength of 2.4 GHz Wi-Fi?
About 12.49 cm in free space.
How do I convert wavelength to frequency?
f = c ÷ λ. For example, 500 nm light is about 599.6 THz.
Why is the wavelength shorter in a cable?
Waves travel slower in the cable, by its velocity factor, so λ = v × c ÷ f.
Check the assumptions and units before relying on a result. Financial, tax and health estimates do not replace advice for your individual circumstances.
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