Frequency Converter
Convert Hertz (Hz), Kilohertz (kHz), Megahertz (MHz), Gigahertz (GHz), RPM, and rad/s.
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Relative Value
*Diagram shows values relative to the selected base unit (Hertz).
Unit Information
What is Hertz (Hz)?
Hertz (symbol: Hz) is the SI unit of frequency, defined as one cycle per second. It is named after Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz is used to measure wave frequencies, such as sound waves, electromagnetic waves (radio, light), and the clock speeds of electronic devices.
What is Megahertz (MHz)?
Megahertz (symbol: MHz) is a multiple of the hertz unit, equal to one million (10⁶) hertz. It's commonly used to express the frequencies of radio waves (e.g., FM radio broadcasts), television signals, and the clock speeds of older computer processors and microcontrollers. For example, an FM radio station might broadcast at 100 MHz.
What are Kilohertz (kHz), Gigahertz (GHz), and Terahertz (THz)?
Kilohertz (kHz) is 1,000 Hz, used for AM radio and some medium-frequency applications. Gigahertz (GHz) is one billion (10⁹) Hz, used for Wi-Fi, cell phones, satellite communications, and modern CPU clock speeds. Terahertz (THz) is one trillion (10¹²) Hz, a range of frequencies between microwaves and infrared light used in advanced imaging and sensing research.
What are Revolutions Per Minute (RPM)?
RPM is a unit of rotational speed, indicating the number of full rotations a mechanical component completes in one minute. It's widely used for engines, motors, and hard drives. To convert RPM to Hz, you divide by 60.
What are Radians per second (rad/s)?
Radians per second is the standard unit of angular frequency (ω). It describes the rate of change of an angle. One full revolution is 2π radians. Therefore, a frequency of 1 Hz is equivalent to 2π rad/s. This unit is essential in physics and engineering for describing circular motion and wave phenomena.
Formulas
1 MHz = 1,000,000 Hz
One megahertz is equal to one million Hertz.
1 GHz = 1,000 MHz
One gigahertz is equal to one thousand Megahertz.
1 RPM = 1/60 Hz ≈ 0.0167 Hz
One revolution per minute is equal to 1/60th of a Hertz.
1 Hz = 2π rad/s ≈ 6.283 rad/s
One Hertz is equivalent to 2π radians per second.
f = c / λ
For electromagnetic waves, frequency (f) is the speed of light (c) divided by wavelength (λ).
T = 1 / f
The period (T) of a wave, in seconds, is the reciprocal of its frequency (f) in Hertz.
Key Reference Points
- AC power line frequency (US): 60 Hz.
- AC power line frequency (Europe/most of world): 50 Hz.
- Middle C note on a piano: ~261.6 Hz.
- Standard FM radio band: 88 MHz to 108 MHz.
- Wi-Fi (2.4 GHz band): Frequencies around 2.4 Gigahertz.
- A car engine idling: ~800 RPM (approx. 13.3 Hz).
- A typical 7200 RPM computer hard drive: 120 Hz.
- Lowest note on a standard piano (A0): ~27.5 Hz.
- Highest note on a standard piano (C8): ~4186 Hz (4.186 kHz).
- Visible light frequency: Approx. 430 THz (red) to 750 THz (violet).
Did You Know?
The range of frequencies humans can typically hear is about 20 Hz to 20,000 Hz (20 kHz). Frequencies below 20 Hz are called infrasound, and those above 20 kHz are ultrasound. Different animals have different hearing ranges; for example, dogs can hear up to 45 kHz and bats up to 120 kHz or more.
The Doppler effect is the change in frequency of a wave (like sound or light) in relation to an observer who is moving relative to the wave source. It's why a siren sounds higher pitched as it approaches and lower pitched as it moves away.
Resonance occurs when an object or system is forced to vibrate at its natural frequency, leading to a dramatic increase in amplitude. This principle is used in musical instruments and can also cause structures to fail if not accounted for in engineering.
For any wave, frequency is inversely proportional to its wavelength. The higher the frequency, the shorter the wavelength, and vice versa. Their product is the wave's velocity (v = fλ).
In music, the pitch of a note is determined by its fundamental frequency. For example, the standard tuning for the 'A' note above middle C (A4) is 440 Hz. Doubling the frequency raises the pitch by one octave.
The refresh rate of a computer monitor, measured in Hertz (Hz), indicates how many times per second the screen image is updated. A 60 Hz monitor refreshes 60 times per second, while a 144 Hz gaming monitor refreshes 144 times, providing smoother motion.
The modern definition of the second is based on the frequency of an atomic transition in cesium-133 atoms, which oscillates at a frequency of exactly 9,192,631,770 Hz. This provides an incredibly stable and precise time standard.
Radio communication uses specific frequency bands for different purposes. For example, AM radio broadcasts are in the kilohertz (kHz) range, while FM radio is in the megahertz (MHz) range, and Wi-Fi and satellite communications use the gigahertz (GHz) range.
The clock speed of a computer's central processing unit (CPU) is measured in Gigahertz (GHz). A 3 GHz processor performs 3 billion cycles per second. While a key metric, it's not the only factor determining a processor's overall performance.
The Schumann resonances are a set of spectrum peaks in the extremely low frequency (ELF) portion of the Earth's electromagnetic field spectrum. They are global electromagnetic resonances, generated and excited by lightning discharges in the cavity formed by the Earth's surface and the ionosphere.
This is the frequency at which an intermittent light stimulus appears to be completely steady to the human eye. It's why a 60 Hz monitor refresh rate looks like a continuous image to most people.
Engineers study the vibrational frequencies of structures like bridges and buildings to ensure they don't match potential external frequencies (like from wind or earthquakes), which could cause resonance and structural failure.
The Bark scale is a psychoacoustical scale of frequency. It's based on the subjective perception of pitch, where equal distances on the Bark scale correspond to equal perceived pitch distances, which is different from the physical Hz scale.
The precise frequency of most modern electronics, from watches to computers, is governed by a quartz crystal oscillator. When a voltage is applied, the crystal vibrates at a very specific and stable frequency due to the piezoelectric effect.
Whales communicate using very low-frequency sounds (infrasound) that can travel for hundreds of miles through water. In contrast, dolphins use high-frequency clicks (ultrasound) for echolocation to navigate and find prey.
The period (T) of a wave is the time it takes to complete one full cycle. It is the reciprocal of frequency (f). A wave with a frequency of 100 Hz has a period of 0.01 seconds.
The frequency of AC electrical grids (50 Hz or 60 Hz) must be kept extremely stable. Deviations can cause clocks to run fast or slow and can lead to grid instability or blackouts if not corrected.
When two sound waves of slightly different frequencies are played together, they produce a phenomenon called 'beats'—a periodic variation in volume whose frequency is equal to the difference between the two original frequencies. Musicians use this to tune instruments.