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Frequency Converter

Convert frequency and rotational speed units instantly in your browser.

A CPU clock is quoted in GHz, a radio station in MHz, a motor's speed in rpm — frequency and rotational speed are two ways of describing similar things. This tool converts between Hz, kHz, MHz, GHz and rpm using decimal steps of 1000 and the strict definition of 1 rpm = 1/60 Hz; the anchors are 1 GHz = 10^9 Hz and 3000 rpm = 50 Hz, the synchronous speed of a motor on a 50 Hz supply.

Note that rpm is a speed of rotation rather than a frequency, so converting it means dividing by 60 — a 2400 rpm drive is 40 Hz. The audio range runs from 20 Hz to 20 kHz, and the 2.4 GHz and 5 GHz of WiFi are band centre frequencies. The arithmetic is simple; the risk is treating an rpm figure as though it were Hz.

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How to use

  1. Enter the frequency or rotational speed.
  2. Read the equivalents in the other units.
  3. Divide rpm by 60 to reach Hz.
  4. Keep band labels such as 2.4 GHz distinct from the value being converted.

How it works

Frequency conversion factors

Frequency is the number of oscillations or occurrences per second, in hertz (Hz). Within SI it's strictly decimal 1000: 1 kHz = 1000 Hz, 1 MHz = 1000 kHz, 1 GHz = 1000 MHz — don't confuse it with the 1024-based storage convention.

RPM and frequency

Mechanical speed rpm is revolutions per minute; dividing by 60 gives Hz: 3000 rpm = 50 Hz. China's mains at 50 Hz exactly matches the synchronous speed of a two-pole motor at 3000 rpm — why inverters and motor nameplates often show both rpm and Hz.

Common frequency references

Common references: China's mains 50 Hz (3000 rpm); a CPU clock at 3.0 GHz = 3000 MHz; a 7200 rpm hard drive = 120 Hz; the human hearing range is about 20 Hz to 20 kHz.

Code example

JavaScript Hz as the hub; rpm divides by 60 

const HZ = { Hz: 1, kHz: 1e3, MHz: 1e6, GHz: 1e9, rpm: 1 / 60 };

const convert = (v, from, to) => v * HZ[from] / HZ[to];

convert(3000, "rpm", "Hz");    // 50 (grid synchronous speed)
convert(2.4, "GHz", "MHz");    // 2400

Python The same coefficients in Python 

HZ = {"Hz": 1, "kHz": 1e3, "MHz": 1e6, "GHz": 1e9, "rpm": 1 / 60}

convert = lambda v, f, t: v * HZ[f] / HZ[t]

convert(50, "Hz", "rpm")       # 3000.0
convert(88, "MHz", "Hz")       # an FM station at 8.8e7 Hz

FAQ

Why does 3000 rpm equal 50 Hz?

rpm is revolutions per minute; dividing by 60 gives revolutions per second, i.e. Hz: 3000 / 60 = 50 Hz. China's 50 Hz mains matches 3000 rpm, the origin of a two-pole induction motor's synchronous speed.

Are Hz, kHz, MHz and GHz 1000x or 1024x?

All 1000x (decimal SI): 1 kHz = 1000 Hz, 1 MHz = 1000 kHz, 1 GHz = 1000 MHz. Don't mix with the 1024 convention for storage — frequency is strictly decimal.

Is a memory module's 3200 MHz the same as a CPU's 3.2 GHz?

Numerically equal but different in meaning: a CPU clock is clock cycles per second; a memory "3200 MHz" usually means the effective data-transfer rate (the actual clock is 1600 MHz with DDR double data rate) and isn't directly comparable for performance.

What does a 144 Hz monitor mean?

The screen refreshes 144 times per second, i.e. 144 Hz; 60 Hz, 120 Hz and 165 Hz are also common. A higher refresh rate smooths motion but stresses the GPU more.

What frequency range can humans hear?

Normal hearing spans about 20 Hz to 20 kHz, with the upper limit dropping with age (adults are often below 16 kHz). Above 20 kHz is ultrasound, below 20 Hz infrasound — generally inaudible but possibly felt as vibration.

Why do China and the US use different mains frequencies?

China and Europe mostly use 50 Hz; the US and parts of Japan use 60 Hz — a historical standard from differing early power-industry paths. Frequency affects motor speed and transformer design, so check an appliance's nameplate for compatibility when traveling.

Are the frequency values I enter recorded?

No. Frequency conversion is just multiplying or dividing by a constant, entirely local in the browser with no network request. History is written only to local storage, clearable in one click; an incognito window leaves no trace on close.