Megahertz to hertz: the FM dial in full
What this conversion does
It multiplies by a million, expanding a radio dial reading into whole cycles per second. The tuner in a car stereo and the transmitter on a hill are describing the same wave, and the two are quoted in different units often enough that the conversion is worth having to hand. Because the factor is a power of ten, no precision is lost in either direction.
Why a dial is numbered in megahertz
The FM broadcast band occupies 87.5 to 108 MHz, which is twenty and a half million hertz of width. Numbered in hertz, every station would be an eight-digit figure and tuning would mean reading digits aloud; numbered in megahertz, the whole band is a short dial from 88 to 108 with the decimal place doing the fine tuning. Nothing about the broadcast changed when the label did.
Megahertz to hertz conversion table
Stations from the bottom of the FM band to the top, with the hertz figures laid out so the pattern of a million to one is easy to verify.
| Megahertz (MHz) | Hertz (Hz) |
|---|---|
| 1 | 1000000 |
| 10 | 10000000 |
| 88.5 | 88500000 |
| 100 | 100000000 |
| 900 | 900000000 |
| 2400 | 2400000000 |
The decimal point carries the fine tuning
FM channels in most of the world are spaced two hundred kilohertz apart, which is 0.2 of a megahertz. That is why a dial reading almost always has one decimal place: 98.5 and 98.7 are different stations, and the digit after the point is the only thing distinguishing them. Written in hertz, the same two stations differ by 200,000, and a dropped zero changes which one you are describing.
Million, not thousand
The step from megahertz to hertz skips over kilohertz entirely, so the multiplier has six zeroes rather than three. The quick check is the digit count: a dial reading in the nineties comes out as a nine-digit hertz figure, not a six-digit one.
Frequently asked questions
How do I convert megahertz to hertz?
Multiply by one million. A station at 98.5 MHz broadcasts at 98,500,000 Hz. The multiplication moves the decimal point six places to the right, so a dial reading with one decimal place becomes a whole number of hertz.
What is 100 MHz in hertz?
Exactly 100,000,000 Hz. The round figure is a convenient landmark rather than an actual station — real FM channels in most countries sit on odd tenths, so 99.9 and 100.1 are more likely dial positions than 100.0.
Why does FM use megahertz while AM uses kilohertz?
Because the two bands are a thousand times apart and each unit keeps its own band to a readable number of digits. AM runs from about 530 to 1700 kilohertz; FM runs from about 88 to 108 megahertz. Using one unit for both would force one of the dials to carry extra zeroes.
Does the converter handle a fractional dial reading?
Yes. A value such as 98.5 or 107.9 converts exactly, and so does a reading with more decimals than any real dial shows. The result is shown in full rather than rounded, so a half-hertz offset stays visible.
Is a frequency in hertz always a whole number?
Not necessarily, though broadcast carriers are chosen to be. A signal at 0.5 MHz is 500,000 Hz exactly, but a frequency of 0.0000001 MHz is 0.1 Hz, which the converter shows as a decimal rather than rounding away.