Frequency Converter
Frequency measures how many times something repeats each second. This converter translates a single value across the full hertz scale (Hz to THz), rotational speed (rpm, rps, rph) and angular frequency (rad/s, deg/s), shows the matching period, and can read out a wavelength for light or sound, so you can move between audio, radio, rotational and wave problems without manual arithmetic.
Formula
Worked example
Convert 1,200 rpm to hertz: 1,200 ÷ 60 = 20 Hz, which is 20 × 2π = 125.7 rad/s and a period of 0.05 s. To go the other way, 50 Hz × 60 = 3,000 rpm.
What frequency means
Frequency counts how many complete cycles of a repeating event occur in one second, and its SI unit is the hertz (Hz), named after physicist Heinrich Hertz. A cycle can be a sound-pressure oscillation, a radio wave, an alternating current, or one full turn of a spinning shaft. Because frequency and the period of one cycle are reciprocals, a 50 Hz signal repeats every 0.02 seconds. Higher frequencies pack more cycles into the same second, which is why pitch rises with frequency in audio and why radio bands climb into the megahertz and gigahertz ranges, with optical and infrared waves reaching terahertz.
Metric prefixes and rotational speed
The kilo, mega, giga and tera prefixes each multiply by a thousand, so 1 kHz is 1,000 Hz, 1 MHz is 1,000,000 Hz, 1 GHz is 1,000,000,000 Hz and 1 THz is a trillion Hz. These steps make it easy to scale between human hearing (roughly 20 Hz to 20 kHz), FM radio (around 100 MHz), Wi-Fi or processor clocks (several GHz), and optical signals (hundreds of THz). Rotational frequency is the same idea applied to spinning: revolutions per second (rps) already equals hertz, revolutions per minute (rpm) divides by 60, and revolutions per hour (rph) divides by 3,600. A 3,000 rpm motor therefore turns at exactly 50 Hz, or 50 rps.
Angular frequency, period and wavelength
Angular frequency describes how fast the phase of an oscillation advances and is measured in radians per second. Because one full cycle is 2π radians, you multiply frequency in hertz by 2π to get rad/s, or by 360 to get degrees per second. The period is simply the reciprocal of frequency, the time for one complete cycle. Turn on the wavelength readout to apply the wave equation lambda = v / f: with the speed of light it gives the wavelength of a radio or optical wave, with the speed of sound (about 343 m/s in air) it gives the wavelength of an acoustic wave, and a custom speed handles other media such as water. These extra outputs let the same tool serve wave physics, signal processing and rotating machinery.
Common frequency unit equivalents
| Unit | Symbol | Value in hertz |
|---|---|---|
| Hertz | Hz | 1 Hz |
| Kilohertz | kHz | 1,000 Hz |
| Megahertz | MHz | 1,000,000 Hz |
| Gigahertz | GHz | 1,000,000,000 Hz |
| Terahertz | THz | 1,000,000,000,000 Hz |
| Revolutions per second | rps | 1 Hz |
| Revolutions per minute | rpm | 0.01667 Hz (1 ÷ 60) |
| Revolutions per hour | rph | 0.0002778 Hz (1 ÷ 3,600) |
| Radians per second | rad/s | 0.15915 Hz (1 ÷ 2π) |
| Degrees per second | deg/s | 0.002778 Hz (1 ÷ 360) |
Metric prefixes scale by 1,000; rotational and angular units relate to hertz as shown.
Frequently asked questions
How do I convert hertz to rpm?
Multiply the frequency in hertz by 60, because one minute contains sixty seconds. For example, 25 Hz equals 25 × 60 = 1,500 rpm. To convert rpm back to hertz, divide by 60. Revolutions per second (rps) is identical to hertz, so no conversion is needed there.
What is the difference between Hz and kHz, MHz, GHz and THz?
They are the same unit scaled by metric prefixes. 1 kHz is 1,000 Hz, 1 MHz is one million Hz, 1 GHz is one billion Hz, and 1 THz is one trillion Hz. Each step up multiplies the number of cycles per second by 1,000.
How is angular frequency (rad/s) related to frequency in Hz?
Angular frequency omega equals 2π times the frequency in hertz, because one full cycle sweeps 2π radians. So 50 Hz is 50 × 2π = 314.16 rad/s. Dividing rad/s by 2π gives the frequency back in hertz.
How do I get the wavelength from a frequency?
Use the wave equation lambda = v / f, where v is the wave speed. Turn on the wavelength option and pick the speed of light for radio or optical waves, the speed of sound for audio, or a custom speed for another medium. For example, a 100 MHz FM signal has a wavelength of about 3 m in air.