Question 1

How do I convert Hz to kHz?

Accepted Answer

Divide hertz by 1,000: kHz = Hz / 1,000. For example, 5,000 Hz / 1,000 = 5 kHz. To convert back, multiply kilohertz by 1,000. Every SI prefix step (Hz, kHz, MHz, GHz, THz) is a factor of 1,000, so you only ever multiply or divide by powers of 1,000.

Question 2

What is a hertz?

Accepted Answer

A hertz (Hz) is the SI unit of frequency: one cycle per second. It applies to anything periodic — a 50 Hz mains supply completes 50 voltage cycles per second, a 440 Hz tone vibrates 440 times per second, and a 2.4 GHz Wi-Fi signal oscillates 2.4 billion times per second. The unit is named after physicist Heinrich Hertz.

Question 3

How many hertz are in a kilohertz?

Accepted Answer

Exactly 1,000 hertz. The prefix kilo- always means 1,000 in SI frequency units: 1 kHz = 1,000 Hz, 1 MHz = 1,000,000 Hz, 1 GHz = 1,000,000,000 Hz, and 1 THz = 1,000,000,000,000 Hz.

Question 4

How many megahertz are in a gigahertz?

Accepted Answer

Exactly 1,000 megahertz. Divide megahertz by 1,000 to get gigahertz: 2,400 MHz / 1,000 = 2.4 GHz. Multiply gigahertz by 1,000 to go the other way: 5 GHz = 5,000 MHz.

Question 5

What is millihertz (mHz)?

Accepted Answer

One millihertz is one-thousandth of a hertz (1 mHz = 0.001 Hz): one cycle every 1,000 seconds. It is used for very slow periodic events, such as the Earth's rotation (about 0.0116 mHz) or long-period seismic waves.

Question 6

How do I convert rpm to Hz?

Accepted Answer

Divide revolutions per minute by 60: Hz = rpm / 60. For example, 120 rpm / 60 = 2 Hz, and 3,000 rpm / 60 = 50 Hz. To convert back, multiply hertz by 60: 50 Hz = 3,000 rpm. This is pure mechanical rotation — one revolution per second equals one hertz.

Question 7

What is the difference between rpm-to-Hz and motor frequency?

Accepted Answer

Mechanical rpm-to-Hz is simply rpm / 60. For an AC induction motor, the electrical supply frequency also depends on the pole count: f = (poles x rpm) / 120. A 1,800 rpm 4-pole motor therefore runs on 60 Hz (4 x 1,800 / 120), which is exactly the US mains frequency. The synchronous speed formula is the reverse: rpm = 120 x f / poles, so a 50 Hz 2-pole motor spins at 3,000 rpm.

Question 8

How do I convert Hz to rad/s?

Accepted Answer

Multiply by 2(pi): angular frequency (omega) = 2 x pi x f. A 60 Hz signal has an angular frequency of about 377 rad/s, and 50 Hz is about 314 rad/s. Angular frequency in radians per second is preferred in AC circuit analysis, vibration, and control systems because phase angles are naturally measured in radians. To convert back: f = omega / (2 x pi).

Question 9

How do I calculate frequency from the period?

Accepted Answer

Use f = 1 / T, where T is the period (time for one cycle) in seconds. A 50 Hz mains cycle has a period of 1/50 = 0.02 s (20 ms); a 60 Hz cycle is 1/60 = 16.67 ms. A 5 ms period gives 1/0.005 = 200 Hz. Conversely, the period is T = 1/f.

Question 10

How do I calculate wavelength from frequency?

Accepted Answer

Use (lambda) = v / f, where v is the wave speed in the medium. For radio and light in a vacuum, v is the speed of light (299,792,458 m/s). A 2.4 GHz Wi-Fi signal in air has a wavelength of about 12.5 cm. For sound, use the speed of sound in the medium instead (343 m/s in air at 20 C): a 440 Hz tone spans about 78 cm in air.

Question 11

Why does the medium change the wavelength but not the frequency?

Accepted Answer

Frequency is set by the source and never changes when a wave crosses into a new medium. The wave speed v does change (light slows in water or fiber; sound travels faster in water than air), and since (lambda) = v / f, the wavelength stretches or compresses to match. This calculator therefore asks you to pick the medium — or enter a custom wave speed — before computing wavelength.

Question 12

What is the Nyquist frequency?

Accepted Answer

The Nyquist frequency is half the sampling rate (fN = fs / 2): the highest signal frequency a digital system can represent without distortion. CD audio samples at 44.1 kHz, so its Nyquist frequency is 22.05 kHz — just above the 20 kHz limit of human hearing. The related Nyquist rate is the minimum sampling rate that avoids aliasing: fs = 2 x fmax.

Question 13

What is aliasing and how do I avoid it?

Accepted Answer

Aliasing happens when a signal is sampled slower than the Nyquist rate (fs < 2 x fmax): high frequencies fold back and appear as false low frequencies. A 7 kHz tone sampled at 10 kHz shows up at 3 kHz. To avoid it, sample at least twice the highest frequency in the signal — and in practice use an anti-aliasing low-pass filter below fs/2, because real signals always contain some higher-frequency content.

Question 14

Why do some countries use 50 Hz and others 60 Hz for mains power?

Accepted Answer

History. The US standardized on 60 Hz (Tesla/Westinghouse systems) while Europe standardized on 50 Hz. Both work; 60 Hz allows slightly smaller transformers, 50 Hz is marginally better for long-distance transmission. Most of the world (Europe, Asia, Africa, Australia, Indonesia) uses 50 Hz; the Americas, Japan (west), and Saudi Arabia use 60 Hz. Modern dual-rated equipment is designed to accept both.

Question 15

What frequency band is 2.4 GHz in?

Accepted Answer

UHF (ultra-high frequency), which spans 300 MHz to 3 GHz. The 2.4 GHz Wi-Fi/Bluetooth band sits at the top of UHF; the 5 GHz Wi-Fi band (5.15-5.825 GHz) sits in SHF (super-high frequency, 3-30 GHz). FM radio at 88-108 MHz is VHF, AM radio at 530-1700 kHz is MF, and GPS L1 at 1575.42 MHz is UHF.

Question 16

How is this different from other unit converters on this site?

Accepted Answer

This tool covers only the frequency and wave family: Hz/kHz/MHz/GHz/THz/mHz plus rpm, rad/s and deg/s, and the wave calculators built on them (period, wavelength, angular frequency, motor speed, Nyquist/aliasing). It does not duplicate the electrical-unit converter (#282, volts/amps/ohms and Ohm's law), the power-unit converter (#284, watts and dBm), the charge converter (#285, coulombs), or the voltage converter (#287, volts and dividers) — each of those covers a different physical quantity. It also replaces several thin single-pair pages (hz-mhz-khz, hz-to-seconds, wavelength-to-frequency, watts-to-hz) with one complete hub.

Unit	1 Hz equals
millihertz (mHz)	1,000 mHz
kilohertz (kHz)	0.001 kHz
megahertz (MHz)	0.000001 MHz
gigahertz (GHz)	1 × 10⁻⁹ GHz
terahertz (THz)	1 × 10⁻¹² THz
radians/second	6.283185 rad/s
revolutions/minute	60 rpm
degrees/second	360 deg/s

Country / region	Mains	Typical voltage
Indonesia, Malaysia, Singapore	50 Hz	220–240 V
United Kingdom, European Union	50 Hz	230 V
Australia, India, China	50 Hz	220–240 V
United States, Canada	60 Hz	120 V
Brazil, Saudi Arabia	60 Hz	127–220 V
Japan	50 / 60 Hz (east / west)	100 V

Source	Frequency
Human heartbeat	≈ 1–1.7 Hz
Human hearing	20 Hz – 20 kHz
Concert pitch A4	440 Hz
AM radio	530 – 1,700 kHz
FM radio	88 – 108 MHz
NFC / contactless	13.56 MHz
GPS L1	1,575.42 MHz
Wi-Fi / Bluetooth / microwave oven	2.4 GHz
Wi-Fi 5 GHz	5.15 – 5.825 GHz
Visible light (red–violet)	430 – 770 THz

Frequency Converter & Wave Calculator

Frequency unit converter — every pair, both directions

Period ⇄ frequency — f = 1/T

Wavelength ⇄ frequency — λ = v/f

Angular frequency & motor speed

Nyquist frequency & aliasing

Band finder — where does this frequency live?

Worked examples

Example 1 — 50 Hz mains: period, angular frequency, motor speed

Example 2 — 2.4 GHz Wi-Fi wavelength

Example 3 — Why CD audio is 44.1 kHz

Reference tables

1 Hz equals

ITU radio spectrum bands

Mains frequency by country (50 Hz vs 60 Hz)

Everyday frequency landmarks

Methodology & scope

Formulas used

Constants

Scope boundary (anti-cannibalization)

Limitations

Frequently asked questions

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