megahertzes

Megahertz, abbreviated MHz, is a unit of frequency equal to one million hertz. The hertz, symbol Hz, is the SI unit of frequency, and the prefix mega- denotes 10^6; thus 1 MHz = 1,000,000 Hz. The megahertz is widely used to describe oscillation rates in electronics and radio systems, including processor clocks, radio transmissions, and communication bands.

In computing, processor clock speeds were commonly expressed in megahertz in the early generations of personal computers, but modern CPUs are typically described in gigahertz. In radio, many bands are measured in megahertz, such as the FM broadcast band around 88–108 MHz, and various VHF amateur and commercial bands. Megahertz can also describe the frequency of clocks in microcontrollers, timing circuits, and memory interfaces, where tens to hundreds of MHz are common in embedded designs. Because MHz is a scaled unit of Hz, it remains compatible with SI conventions and measurements; the base unit is still the hertz.

The term megahertzes is nonstandard; the correct plural form is megahertz, and MHz is used to denote both singular and plural quantities. The concept is named after Heinrich Hertz, the physicist who demonstrated electromagnetic waves. Measurement of frequency in MHz typically uses frequency counters or spectrum analyzers, which can resolve cycles per second at these scales.