Frequency Converter Guide: Hz, kHz, MHz, GHz, and RPM

Frequency measures how many times something repeats per second, and it shows up in wildly different contexts: a car engine's RPM, a CPU's clock speed, an FM radio dial, and the vibration rate of a guitar string all boil down to the same unit family. The prefixes, kilo, mega, giga, are what make the numbers manageable, but they're also where mistakes creep in.

Hertz: One Cycle Per Second

One hertz (Hz) equals one cycle per second. Standard AC electrical power in the US runs at 60 Hz, meaning the current reverses direction 60 times every second. Most of Europe and Asia runs on 50 Hz power. This 10 Hz difference is why some appliances, particularly ones with motors or clocks tied to mains frequency, behave differently or need a voltage and frequency converter when moved between regions.

The Metric Prefixes, Precisely

Converting between them is just moving the decimal point by the right number of places. A CPU running at 3.6 GHz operates at 3.6 x 1,000,000,000 = 3,600,000,000 Hz, or equivalently 3,600 MHz, or 3,600,000 kHz. When comparing an older 2,400 MHz processor spec to a newer 3.2 GHz one, convert both to the same unit first: 2,400 MHz equals 2.4 GHz, so the newer chip's clock speed is 0.8 GHz higher.

Radio Bands in Context

AM radio broadcasts between roughly 530 and 1,700 kHz. FM radio broadcasts between 88 and 108 MHz, over a thousand times higher in frequency than AM, which is part of why FM supports better audio fidelity. Household Wi-Fi commonly runs on 2.4 GHz or 5 GHz bands; the 5 GHz band carries data faster over shorter range because the higher frequency allows more bandwidth but penetrates walls less effectively than 2.4 GHz.

Frequency and Wavelength Are Linked

Frequency and wavelength are inversely related through the speed of light: wavelength = speed of light / frequency. For a 100 MHz FM signal, wavelength = 300,000,000 m/s / 100,000,000 Hz = 3 meters. For a 2.4 GHz Wi-Fi signal, wavelength = 300,000,000 / 2,400,000,000 = 0.125 meters, or 12.5 centimeters. This is why higher-frequency signals need physically smaller antennas.

RPM Is a Frequency Too

Revolutions per minute (RPM) measures rotational frequency, and it converts directly to hertz since hertz is cycles per second: Hz = RPM / 60. A car engine idling at 800 RPM is completing 800/60 = 13.3 rotations per second, or 13.3 Hz. A hard drive spinning at 7,200 RPM completes 7,200/60 = 120 rotations per second. Going the other direction, a fan motor rated at 60 Hz AC synchronous speed on a 2-pole motor spins at roughly 60 x 60 = 3,600 RPM.

A Worked Conversion Chain

Suppose a spec sheet lists a microcontroller's clock at 16,000,000 Hz and you need to compare it to a competitor's chip listed at 20 MHz. Convert the first to MHz: 16,000,000 / 1,000,000 = 16 MHz. Now the comparison is direct: 20 MHz is 4 MHz, or 25%, faster than 16 MHz. Mixing raw Hz with MHz specs side by side is a common source of confusion in datasheets, so converting to a shared unit before comparing avoids that mistake.

Convert Any Frequency in Seconds

Between Hz, kHz, MHz, GHz, and RPM, keeping track of the zeros by hand is where errors happen. The frequency converter on this site handles all of these units directly, so whether you're comparing processor clock speeds, checking a radio frequency, or converting motor RPM to hertz, you get an accurate number without counting zeros yourself.