All Frequency Units

How to Convert Frequency Units?

Frequency measures the number of cycles or oscillations per unit of time. This converter uses standard SI prefixes to convert between hertz, kilohertz, megahertz, gigahertz, and revolutions per minute.

Enter a value, select your source unit, and choose the target unit. The converter displays all unit equivalents simultaneously for easy reference.

Frequently Asked Questions

What units does this frequency converter handle?

This converter handles the four standard SI-prefixed frequency units (Hz, kHz, MHz, GHz) plus revolutions per minute (RPM). Hertz is the SI unit equal to one cycle per second, defined as the inverse of the SI second. The prefixes follow strict decimal scaling: 1 kHz = 10^3 Hz, 1 MHz = 10^6 Hz, 1 GHz = 10^9 Hz. RPM is included because it's the dominant rotational-frequency unit in mechanical engineering, automotive, and industrial contexts. The converter does not include obsolete or domain-specific units such as cycles per second (cps, deprecated 1960), angular frequency in rad/s, or wavenumber in cm^-1; those require additional context to convert correctly.

What is the exact conversion factor between Hz and RPM?

1 Hz equals exactly 60 RPM, because one cycle per second is sixty cycles per minute. Conversely, 1 RPM equals exactly 1/60 Hz, which is approximately 0.01666... Hz. The factor is exact because both definitions ultimately rest on the SI second. So a turntable running at 33 1/3 RPM is exactly 0.5555... Hz, and a car engine at 6000 RPM is exactly 100 Hz. Note that RPM measures rotational frequency, not angular frequency; to convert RPM to angular frequency in rad/s, multiply by 2*pi/60, giving approximately 0.10472.

When should I use kHz vs MHz vs GHz?

Use kHz for audio (human hearing 20 Hz to 20 kHz, CD sampling at 44.1 kHz), AM radio (530 to 1700 kHz), and ultrasound below 1 MHz. Use MHz for FM radio (88 to 108 MHz), VHF/UHF television, early CPUs, and medical ultrasound (1 to 18 MHz). Use GHz for modern CPUs (2 to 5 GHz), Wi-Fi (2.4 GHz, 5 GHz, 6 GHz), 5G cellular (3.5 GHz to mmWave 28+ GHz), satellite communications, and radar. As a rule of thumb, pick the prefix that keeps the numeric value between 1 and 1000 to maximize readability and avoid ambiguous exponents in technical writing.

How precise are the conversions, and how should I round?

Internally, conversions use 64-bit floating-point arithmetic, giving about 15 to 17 significant decimal digits of precision. For metric-to-metric prefix changes (Hz to kHz to MHz), the conversion is exact in decimal because the factor is a power of ten; rounding error only enters when displaying. For RPM conversions the factor 60 is also exact. In practice, display 4 to 6 significant figures for engineering work and 2 to 3 for casual use. Avoid showing more digits than your input justifies: if you measured 100 Hz to 2 significant figures, presenting 6000.000 RPM implies false precision.

Why does my measured frequency disagree with the nominal value?

All real oscillators drift. Crystal oscillators typically have +/-20 to +/-100 parts per million (ppm) tolerance, meaning a nominal 10 MHz crystal may actually run at 9.999 to 10.001 MHz. Temperature, aging, and load capacitance all shift the actual frequency. Mains power is nominally 50 or 60 Hz but instantaneously varies by +/-0.5 Hz under load; the long-term average is held tight by grid operators. For high-precision work, GPS-disciplined oscillators (GPSDO) and rubidium standards reach 10^-11 stability. The converter assumes your input is exact; if you suspect drift, measure with a frequency counter referenced to a known standard.

What is the difference between frequency and angular frequency?

Frequency f is measured in hertz (cycles per second). Angular frequency omega is measured in radians per second and equals 2*pi*f. They describe the same oscillation but in different mathematical languages: f is natural for counting events, while omega is natural in calculus because sin(omega*t) has derivative omega*cos(omega*t) with no extra factor of 2*pi. A 60 Hz signal has angular frequency 2*pi*60 = 376.99 rad/s. Physics textbooks usually use omega; engineering data sheets and consumer specs almost always use f. This converter operates on f only; multiply or divide by 2*pi if you need omega.

How is hertz defined in the modern SI system?

Hertz is a derived SI unit equal to s^-1, where the second is defined since 1967 as exactly 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom (at 0 K). Since the 2019 SI redefinition, the second remains defined by this caesium transition, but all other base units were redefined in terms of fixed fundamental constants. Hertz, like the second, is therefore one of the most accurately realizable units in physics: primary frequency standards reach fractional uncertainties below 10^-16. NIST in the US and BIPM internationally coordinate the timescales (TAI, UTC) that anchor all frequency measurements.

When does the SI prefix system break down for frequencies?

The SI prefixes cover 10^-30 to 10^30, so they technically span any physical frequency, but practical usage breaks down at extremes. Below 1 Hz, scientists use millihertz (mHz, brain waves, ocean tides), microhertz (geophysical oscillations), and even nanohertz (gravitational-wave backgrounds from supermassive black hole binaries). Above 1 THz (10^12 Hz), the terahertz gap historically lacked good sources and detectors; optical frequencies (~10^14 Hz, visible light) are usually expressed as wavelength in nanometers instead. Gamma-ray frequencies (~10^20 Hz) are virtually always reported as photon energy in MeV or GeV. This converter intentionally limits itself to the kHz-to-GHz electronics range plus RPM, the units 99% of users actually need.

Units

Hertz (Hz)

The hertz is the SI unit of frequency, equal to one cycle per second. Named after Heinrich Hertz, it's used for measuring sound frequencies (human hearing ranges from 20 Hz to 20,000 Hz), electrical signals, and processor clock speeds.

Kilohertz (kHz)

Equal to 1,000 hertz, the kilohertz is commonly used for audio frequencies and AM radio broadcasts. Audio sampling rates are often expressed in kHz, such as 44.1 kHz for CD-quality audio or 48 kHz for professional video.

Megahertz (MHz)

Equal to 1,000,000 hertz, the megahertz measures FM radio frequencies (88-108 MHz), early computer processor speeds, and wireless communication bands. Wi-Fi operates at 2,400 MHz (2.4 GHz) and 5,000 MHz (5 GHz).

Gigahertz (GHz)

Equal to 1,000,000,000 hertz, the gigahertz is the standard unit for modern processor speeds. Current CPUs operate between 2-5 GHz, while 5G cellular networks use frequencies from 0.6 to 39 GHz.

Revolutions Per Minute (RPM)

RPM measures rotational frequency, counting complete rotations per minute. Hard drives spin at 5,400-7,200 RPM, car engines idle at 600-1,000 RPM, and washing machines spin at 800-1,600 RPM during the final cycle.

Common Frequency Conversions