📡 Frequency Converter: Hz, kHz, MHz, GHz, THz, rpm and rad/s

What is the Frequency Converter?

Frequency is the rate at which a repeating event happens, counted per second. The SI unit is the hertz, named after physicist Heinrich Hertz, where one hertz equals one cycle per second. Because real signals span an enormous range, from a few cycles per second up to trillions, engineers use the standard metric prefixes to keep the numbers readable. Kilo means one thousand, mega one million, giga one billion and tera one trillion, 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 1,000,000,000,000 Hz. Each step up the ladder multiplies by exactly one thousand.

Converting between these units is just multiplying or dividing by powers of ten. To go from a larger unit to a smaller one you multiply: 2.4 GHz becomes 2,400 MHz or 2,400,000,000 Hz. To go the other way you divide: 500,000 Hz is 500 kHz or 0.5 MHz. This tool handles that by first turning whatever you type into hertz using a fixed factor for each unit, then dividing that hertz value by the factor of every other unit. Working through a single base unit avoids rounding drift and keeps all the fields exactly in agreement, which is why the result is more reliable than converting from one prefix straight to another.

Revolutions per minute (rpm) is a rotational frequency rather than a wave frequency, but it is still a count of repetitions over time, so it converts cleanly into hertz. The only difference is the time base: rpm counts per minute, not per second. Since a minute holds 60 seconds, one revolution per minute equals one sixtieth of a hertz, so you divide rpm by 60 to get Hz and multiply Hz by 60 to get rpm. A motor spinning at 3,000 rpm is therefore turning at 50 Hz, which is why 50 Hz mains power and 3,000 rpm two-pole motors are so often mentioned together.

Radians per second, written with the Greek letter omega, is the angular frequency. It describes the same motion in terms of the angle swept out rather than whole cycles. Because one full cycle is 2 times pi radians, angular frequency equals 2 times pi times the frequency in hertz. So 1 Hz is about 6.2832 rad/s, and to reverse it you divide rad/s by 2 times pi. Angular frequency shows up throughout physics and signal processing in formulas for waves, oscillators and alternating current, so having it beside the everyday units saves a separate calculation.

Two other quantities are closely tied to frequency even though they use different units. Period is the time for a single cycle and is simply one divided by the frequency, so a 50 Hz signal has a period of 0.02 seconds (20 milliseconds). Wavelength applies to travelling waves and equals the wave speed divided by the frequency; for light and radio in a vacuum that speed is 299,792,458 metres per second, so a 100 MHz FM signal has a wavelength of about 3 metres. Keeping these relationships in mind helps you sanity check any conversion and understand what a frequency really means in the physical world.

When to use it

• Reading a Wi-Fi or Bluetooth spec sheet and converting a 2.4 GHz or 5 GHz band into MHz or Hz.
• Comparing a CPU clock quoted in GHz against a memory or bus speed quoted in MHz.
• Translating a radio station frequency such as 88.5 MHz into hertz for a link-budget or antenna calculation.
• Converting a motor or fan speed in rpm into hertz to match a variable-frequency drive setting.
• Checking audio gear, where the audible range of about 20 Hz to 20 kHz is often discussed in mixed units.
• Turning a frequency in hertz into angular frequency in rad/s for a physics or control-systems formula.

How to use the Frequency Converter

1. Find the unit you already know among the labelled boxes (Hz, kHz, MHz, GHz, THz, rpm or rad/s).
2. Type or paste your value into that box.
3. Read the converted result from every other box, which updates instantly.
4. Clear the box or change the number at any time to run a new conversion.
5. Copy any result you need directly from its field.

Formula & method

Worked examples

Common frequency units expressed in hertz

Quick reference conversions

Everyday frequency bands for context

Common mistakes to avoid

• Mixing up kHz, MHz and GHz by a factor of 1,000. Each step up the prefix ladder is one thousand times larger, not ten or one hundred. 1 GHz is 1,000 MHz and 1,000,000 kHz, so dropping or adding a thousand is the most common slip.
• Treating rpm as if it were already in hertz. Revolutions per minute counts per minute, so you must divide by 60 to reach hertz. Forgetting that gives an answer 60 times too large.
• Confusing frequency with angular frequency. Angular frequency, written with the Greek letter omega, is in radians per second and equals 2 times pi times the frequency in hertz. A 50 Hz signal is about 314 rad/s, so the two numbers are not interchangeable.
• Assuming more digits means more accuracy. A reading like 88.5 MHz is only as precise as its source. Converting it to 88,500,000.0000 Hz does not add real precision, it just adds trailing digits.
• Mixing up period and frequency. Period is the time for one cycle and is the reciprocal of frequency, not the same thing. A higher frequency means a shorter period, so 1,000 Hz has a period of 1 millisecond, not 1,000 seconds.
• Forgetting that wavelength depends on the medium. Wavelength equals wave speed divided by frequency, and that speed changes between vacuum, air, water or a cable. The same frequency does not have a single fixed wavelength everywhere.

Glossary

Hertz (Hz)

The SI unit of frequency, equal to one cycle or repetition per second.

Frequency

How many times a repeating event occurs in one second.

Kilohertz (kHz)

One thousand hertz, often used for audio and low radio frequencies.

Megahertz (MHz)

One million hertz, common for radio broadcasts and bus speeds.

Gigahertz (GHz)

One billion hertz, typical of CPU clocks and wireless bands.

Terahertz (THz)

One trillion hertz, used for infrared light and advanced electronics.

rpm

Revolutions per minute, a rotational frequency equal to one sixtieth of a hertz per revolution per minute.

Angular frequency (rad/s)

Frequency expressed as radians swept per second, equal to 2 times pi times the frequency in hertz.

Period (T)

The time taken for one complete cycle, equal to one divided by the frequency.

Wavelength

The distance one wave cycle covers, equal to the wave speed divided by the frequency.

Frequently asked questions