Wavelength to frequency: why radio bands are named in metres
What this conversion does
It divides the speed of light — 299,792,458 metres per second — by a wavelength to recover the frequency. Radio amateurs and broadcasters named their bands by wavelength long before frequency was easy to display, and the names stuck: the two metre band, the forty metre band, the seventy centimetre band. Converting a band name back into a frequency is what makes it possible to tune a modern radio to it.
A name that is also a measurement
A band name in metres is an approximation, because the band covers a range of wavelengths rather than one. The two metre amateur allocation spans 144 to 148 MHz, which corresponds to wavelengths of about 2.08 down to 2.03 metres. The name rounds that to a memorable figure, so it describes the band well enough to identify it and not precisely enough to tune with.
Wavelength to frequency conversion table
Band names and other familiar wavelengths with the frequencies they correspond to, showing how a rounded name maps onto a range.
| Wavelength (metres) | Megahertz (MHz) |
|---|---|
| 0.125 | 2398.339664 |
| 0.5 | 599.584916 |
| 1 | 299.792458 |
| 2 | 149.896229 |
| 3 | 99.9308193333 |
| 10 | 29.9792458 |
Why the metre naming survived
Building an antenna requires knowing the wavelength, because the element has to be a fraction of it, so wavelength was the quantity early operators worked with directly. Frequency became easy to measure and display much later, and by then the band names were established in legislation, in equipment markings and in everyday speech. The conversion is what lets the older naming continue to be used alongside modern dials.
Divide 300 by the metres
For a quick estimate, divide 300 by the wavelength in metres to get megahertz. Two metres gives about 150 MHz, three metres gives about 100, which is the FM broadcast region, and seventy centimetres gives roughly 430 MHz.
Frequently asked questions
How do I convert a wavelength to a frequency?
Divide the speed of light, 299,792,458 metres per second, by the wavelength in metres. Two metres gives about 149.9 MHz, and seventy centimetres gives about 428 MHz. The converter scales the answer into the unit you choose.
Why is the two metre band called that?
Because its wavelengths are close to two metres. The allocation from 144 to 148 MHz corresponds to wavelengths between roughly 2.08 and 2.03 metres, so the name is a rounded label for the band rather than an exact frequency.
What wavelength does FM radio use?
About three metres. The broadcast band runs from roughly 88 to 108 MHz, which corresponds to wavelengths between about 3.4 and 2.8 metres, and the familiar three metre figure is the round number in the middle.
Does the band name tell me exactly where to tune?
No. It identifies a region of the spectrum, and the actual allocation is defined by its frequency limits in the regulations. Two band names in metres can also overlap without corresponding to the same range, which is why the frequency is the authoritative figure.
Can the converter handle a wavelength below a millimetre?
Yes. Micrometre wavelengths convert to frequencies in the terahertz range, and the tool accepts them without any special handling. Results are scaled to a readable unit rather than being left as long decimals.