Frequency Converter
Frequency measures how many times an event repeats in a given time period, typically per second. The SI unit is the hertz (Hz), where one hertz means one cycle per second. Larger frequencies use SI prefixes: kilohertz (kHz) for thousands, megahertz (MHz) for millions, gigahertz (GHz) for billions, and terahertz (THz) for trillions of cycles per second. Radio stations broadcast in kilohertz or megahertz, WiFi routers operate at gigahertz frequencies, and light oscillates at terahertz frequencies. Rotational machinery often uses revolutions per minute (RPM), where one RPM equals 1/60 hertz. Angular velocity is expressed in radians per second, where one hertz equals 2 pi (about 6.28) radians per second because one full rotation contains 2 pi radians. Converting between frequency units is essential when specifying radio frequencies, computer clock speeds, electrical AC power, vibration analysis, and mechanical equipment performance. A computer processor running at 3 gigahertz executes 3 billion instructions per second. This calculator displays nine frequency units for instant conversion with NIST precision.
NIST conversion factors
All conversions below use standard NIST-defined factors, with all units expressed relative to the hertz.
| Unit | Symbol | Hertz |
|---|---|---|
| Millihertz | mHz | 0.001 |
| Hertz | Hz | 1 |
| Kilohertz | kHz | 1,000 |
| Megahertz | MHz | 1,000,000 |
| Gigahertz | GHz | 1,000,000,000 |
| Terahertz | THz | 1,000,000,000,000 |
| Radians per second | rad/s | 0.15915494 |
| Revolutions per minute | RPM | 0.016667 |
| Revolutions per second | RPS | 1 |
Frequency converter: frequently asked questions
What is the SI unit of frequency?
The hertz (Hz) is the SI unit of frequency, defined as one cycle per second. Named after physicist Heinrich Hertz, one hertz means an event repeats once per second. Larger frequencies use kilohertz (kHz), megahertz (MHz), gigahertz (GHz), and terahertz (THz).
What is the difference between frequency and period?
Frequency is the number of cycles per second (in hertz). Period is the time for one cycle (in seconds). They are reciprocals: period equals 1 divided by frequency. A 100 Hz signal has a period of 0.01 seconds.
What is an RPM?
RPM stands for revolutions per minute, commonly used for rotating equipment like motors and engines. One RPM equals 1/60 hertz. A motor running at 3,600 RPM rotates 60 times per second, or 60 hertz.
What is a radian per second?
Radians per second (rad/s) is another way to express angular frequency. Since 2 pi radians equal one full rotation, one hertz equals 2 pi radians per second (about 6.28 rad/s).
Why are there so many frequency units?
Different fields use different frequency units for practical reasons. Radio uses Hz/kHz/MHz/GHz. Rotational machinery uses RPM. Physics and engineering use rad/s. Converting ensures clarity when comparing specifications across different contexts.
Official sources
- NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices.
- NIST Special Publication 330: The International System of Units.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.