Frequency Converter Guide: Hz, kHz, MHz, GHz & Beyond
Quick Answer
- *1 kHz = 1,000 Hz | 1 MHz = 1,000,000 Hz | 1 GHz = 1,000,000,000 Hz.
- *Frequency × wavelength = speed of light (c = f × λ).
- *Human hearing range: 20 Hz – 20,000 Hz. Most speech: 250 Hz – 4,000 Hz.
- *To convert RPM to Hz, divide by 60. To convert Hz to RPM, multiply by 60.
What Is Frequency?
Frequency measures how many times something repeats per second. The unit is the hertz (Hz), named after physicist Heinrich Hertz who first proved the existence of electromagnetic waves in 1887. One hertz means one cycle per second. A guitar string vibrating 440 times per second produces a 440 Hz tone — the A above middle C.
Frequency shows up everywhere: sound waves, radio signals, CPU clock speeds, AC power, light, and even your heartbeat (about 1–1.7 Hz at rest, or 60–100 beats per minute).
Frequency Unit Conversion Table
All frequency units follow the metric prefix system. Each step up multiplies by 1,000:
| Unit | Symbol | In Hertz | Common Use |
|---|---|---|---|
| Millihertz | mHz | 0.001 Hz | Seismology, ocean waves |
| Hertz | Hz | 1 Hz | Power grid (50/60 Hz), bass audio |
| Kilohertz | kHz | 1,000 Hz | AM radio, audio sampling |
| Megahertz | MHz | 1,000,000 Hz | FM radio, older CPUs |
| Gigahertz | GHz | 10&sup9; Hz | Wi-Fi, modern CPUs, 5G |
| Terahertz | THz | 10¹² Hz | Imaging, spectroscopy |
To convert down (e.g., GHz to MHz), multiply by 1,000. To convert up (e.g., Hz to kHz), divide by 1,000. So 2.4 GHz = 2,400 MHz = 2,400,000 kHz = 2,400,000,000 Hz.
Frequency and Wavelength
Frequency and wavelength are two sides of the same coin. They're connected by the speed of light (for electromagnetic waves) or the speed of sound (for acoustic waves):
λ = c ÷ f
Where λ is wavelength, c is the speed of propagation (299,792,458 m/s for light in vacuum, ~343 m/s for sound in air at 20°C), and f is frequency. As frequency goes up, wavelength goes down.
| Signal | Frequency | Wavelength |
|---|---|---|
| AM radio | 530–1,700 kHz | 176–566 meters |
| FM radio | 88–108 MHz | 2.8–3.4 meters |
| Wi-Fi (2.4 GHz) | 2,400 MHz | 12.5 cm |
| Wi-Fi (5 GHz) | 5,000 MHz | 6 cm |
| 5G mmWave | 24–47 GHz | 6–12 mm |
| Visible light | 430–770 THz | 390–700 nm |
This is why higher-frequency signals have shorter range and struggle with obstacles. A 5 GHz Wi-Fi signal (6 cm wavelength) gets absorbed by walls more than 2.4 GHz (12.5 cm wavelength). According to testing by Cisco, 5 GHz signal strength drops 35–40% faster through drywall compared to 2.4 GHz.
Frequency in Everyday Life
Audio and Music
Human hearing spans 20 Hz to 20,000 Hz(20 kHz), though most adults over 25 lose sensitivity above 16,000 Hz. The musical scale is built on frequency ratios. Middle C is 261.63 Hz. The A above middle C is 440 Hz (the standard tuning reference). Each octave doubles the frequency — A4 is 440 Hz, A5 is 880 Hz, A3 is 220 Hz.
CD-quality audio samples at 44,100 Hz (44.1 kHz) because the Nyquist theorem requires sampling at twice the highest frequency you want to capture. Since we hear up to ~20 kHz, 44.1 kHz captures the full audible range. Hi-res audio uses 96 kHz or 192 kHz, though whether humans can perceive the difference is debated — a 2014 meta-analysis in the Journal of the Audio Engineering Society found no statistically significant difference in blind listening tests.
Computing and Processors
CPU clock speed is measured in GHz. A 4.5 GHz processor completes 4.5 billion clock cycles per second. In 1971, the Intel 4004 ran at 740 kHz. By 2024, desktop processors routinely hit 5.0–6.0 GHzwith turbo boost — roughly an 8,000× increase in 53 years. RAM frequency (e.g., DDR5-6000) also uses MHz, representing data transfer cycles.
Power Grid
North America, most of South America, and parts of Asia use 60 Hz AC power. Europe, Africa, most of Asia, and Australia use 50 Hz. The difference traces back to the 1890s when Westinghouse chose 60 Hz and AEG chose 50 Hz for their respective markets. According to the International Electrotechnical Commission, about 60% of the world's population lives in 50 Hz countries.
Radio and Wireless
The electromagnetic spectrum is allocated by frequency bands. The ITU (International Telecommunication Union) manages global spectrum allocation. As of 2024, the global wireless data market uses over 1,200 GHz of allocated spectrum across cellular, Wi-Fi, satellite, and IoT bands.
Converting Between Hz and RPM
RPM (revolutions per minute) and Hz (cycles per second) both measure rotational frequency but on different time scales:
Hz = RPM ÷ 60
RPM = Hz × 60
A washing machine spin cycle at 1,200 RPM = 20 Hz. A car engine at 3,000 RPM = 50 Hz. The U.S. power grid at 60 Hz means generators spin at 3,600 RPM (or 1,800 RPM for 4-pole generators).
Frequency and Period
Period is the inverse of frequency — it measures the time for one complete cycle:
T = 1 ÷ f
A 1,000 Hz signal has a period of 0.001 seconds (1 millisecond). A 60 Hz power cycle has a period of about 16.7 milliseconds. Your resting heart at 72 BPM (1.2 Hz) has a period of 833 milliseconds between beats.
Convert between any frequency units instantly
Use our free Frequency Converter →Frequently Asked Questions
How many hertz are in a megahertz?
One megahertz (MHz) equals 1,000,000 hertz (Hz). The prefix "mega" means one million. So 2.4 GHz Wi-Fi operates at 2,400 MHz or 2,400,000,000 Hz.
What is the relationship between frequency and wavelength?
Frequency and wavelength are inversely related by the equation: wavelength = speed of light ÷ frequency (λ = c ÷ f). As frequency increases, wavelength decreases. A 100 MHz FM radio signal has a wavelength of about 3 meters, while a 5 GHz Wi-Fi signal has a wavelength of about 6 centimeters.
What frequency range can humans hear?
The human ear can typically hear frequencies between 20 Hz and 20,000 Hz (20 kHz). Most speech falls between 250 Hz and 4,000 Hz. Hearing sensitivity peaks around 2,000–5,000 Hz, which is why alarm tones and baby cries are designed in that range.
What is the difference between Hz and RPM?
Hz (hertz) measures cycles per second, while RPM measures revolutions per minute. To convert RPM to Hz, divide by 60. A motor spinning at 3,600 RPM operates at 60 Hz (3,600 ÷ 60 = 60). This is why the U.S. power grid runs at 60 Hz — generators spin at 3,600 RPM.
Why does the U.S. use 60 Hz power while Europe uses 50 Hz?
The difference is historical. In the 1890s, Westinghouse chose 60 Hz for the U.S. grid because it worked well with their generator and lighting technology. AEG in Germany chose 50 Hz, and most of Europe followed. Both frequencies work fine for appliances, but the difference means some electronics need adapters or dual-voltage support when traveling internationally.