Frequency Unit Converter
Convert between any pair of frequency units — hertz, kilohertz, megahertz, gigahertz, terahertz, revolutions per minute, beats per minute, and radians per second — using conversion factors verified against NIST and BIPM references. Type a value and the result updates instantly.
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What is frequency, and why are there so many units?
Frequency is the rate at which a periodic event repeats — cycles per second. The SI unit is the hertz (Hz), defined as one cycle per second. The same physical quantity describes the 50 Hz alternating current in a wall socket, the 88–108 MHz of FM radio, the 2.4 GHz Wi-Fi band, the 500 THz of green light, the 7200 rpm of a hard-drive platter, and the 120 BPM of a dance track. Whenever something repeats in time, frequency is the right way to describe it.
The reason there are so many frequency units is that periodic phenomena vary across more than twenty-five orders of magnitude. The mains alternates 50 times a second; visible light oscillates 5 × 10¹⁴ times a second. To keep numbers in a comfortable range, engineers reach for SI prefixes (kHz, MHz, GHz, THz). At the same time, mechanical engineers prefer rpm because shafts and motors run at hundreds to tens of thousands of revolutions per minute, and musicians count beats per minute on a metronome. The unit you meet depends on the discipline.
The frequency units, explained
Hertz (Hz) and its multiples — the SI baseline
1 Hz = 1 cycle per second = 1 s⁻¹. Named after Heinrich Hertz, who first proved electromagnetic waves exist in 1887. The kilohertz (kHz, 10³ Hz) covers audio frequencies and AM radio (530–1700 kHz). The megahertz (MHz, 10⁶ Hz) covers FM radio, two-way radio, and older CPU clocks. The gigahertz (GHz, 10⁹ Hz) is the language of mobile phones, Wi-Fi, satellite links, and modern CPU clocks. The terahertz (THz, 10¹² Hz) is used in spectroscopy and the THz gap between microwaves and infrared light. The millihertz (mHz, 10⁻³ Hz) describes very slow oscillations, such as a 0.5 mHz tide cycle (half-day).
Revolutions per minute (rpm)
1 rpm equals 1/60 Hz ≈ 0.01667 Hz. This is the standard unit for rotating mechanical systems. A car engine idles at 700–900 rpm, redlines at 6500–8500 rpm. A hard-disk drive spins at 5400, 7200, or 10 000 rpm. A washing machine spins at 800–1600 rpm during the spin cycle. Although Hz would also work, rpm gives larger, easier numbers for the speeds of shafts and rotors.
Beats per minute (BPM) — music
1 BPM = 1/60 Hz, numerically identical to rpm. Used in music for tempo: 60 BPM = one beat per second, 120 BPM is a common dance/pop tempo, 180 BPM is fast running music, 200+ BPM is drum-and-bass or speed metal. A metronome counts BPM. Heart rate is also commonly given in BPM (60–100 at rest, 150–180 during exercise). The use of BPM rather than rpm or Hz is purely cultural — they are the same unit dressed differently.
Radian per second (rad/s) — physics
Angular frequency ω = 2πf. So 1 rad/s = 1/(2π) Hz ≈ 0.1592 Hz. This is the unit of choice in physics and signal-processing equations: a sinusoid is naturally written as sin(ωt). Mechanical engineers use rad/s for angular velocity of rotating parts when integrating torque or computing centripetal acceleration. Electrical engineers use rad/s in transfer functions and impedance formulas. To convert from rpm to rad/s, multiply by 2π/60 ≈ 0.1047.
Why so many SI prefixes for Hz?
Frequencies span at least 25 orders of magnitude in everyday tech. Power lines: 50 or 60 Hz. AM radio: 530 kHz–1700 kHz. FM radio: 87.5–108 MHz. TV: 50–800 MHz. Wi-Fi: 2.4 GHz / 5 GHz / 6 GHz. Visible light: 430–770 THz. X-rays: 30 PHz–30 EHz. Without prefixes, FM radio would have to be written as 87 500 000 Hz. The k/M/G/T/P chain keeps the human-readable number under 1000.
Real-world applications and which unit to expect
- AC mains and power systems: 50 Hz in Europe, Africa, most of Asia, Australia, much of South America. 60 Hz in North America, parts of South America, Japan (split: 50 Hz in eastern Japan, 60 Hz in western Japan since the late 19th century). Aircraft power: 400 Hz (allows lighter transformers and motors). Higher frequency = smaller, lighter electromagnetic equipment, but more skin-effect loss in long cables.
- Radio broadcasting: AM: 530–1700 kHz (medium wave). Shortwave: 3–30 MHz. FM: 87.5–108 MHz worldwide (Japan: 76–95 MHz). DAB+: 174–240 MHz. TV broadcast: VHF 50–250 MHz, UHF 470–800 MHz. Marine VHF: 156–162 MHz. Aviation VHF: 118–137 MHz. Each band is regulated by the ITU and licensed by national authorities.
- Wi-Fi and mobile: Wi-Fi 4/5 (802.11n/ac): 2.4 GHz and 5 GHz. Wi-Fi 6E and 7: also 6 GHz. Bluetooth: 2.4 GHz. 4G LTE: bands at 700 MHz, 850 MHz, 1.8 GHz, 2.1 GHz, 2.6 GHz. 5G: same low/mid bands plus mmWave 24–47 GHz. Higher frequency means more bandwidth but shorter range and worse penetration.
- CPUs and electronics: Modern desktop CPUs run at 3–6 GHz base clock, with boost frequencies higher. Laptop CPUs 2–5 GHz. Microcontrollers (Arduino) 8–48 MHz. Older 8-bit CPUs (1980s) 1–4 MHz. RAM bus runs at hundreds of MHz to several GHz. PCIe 5.0 transfers at 32 GT/s per lane. The trend has been to slow clock growth and add cores, since power scales roughly with f × V².
- Monitor refresh rate: Display refresh rate is in Hz. 60 Hz is standard (the screen updates 60 times per second). Gaming monitors: 120 Hz, 144 Hz, 240 Hz, 360 Hz. Professional video: 24, 25, 30, 50, 60, 120 Hz. Higher refresh = smoother motion, lower input lag, but more GPU and panel cost.
- Audio: Human hearing: 20 Hz–20 kHz (the upper limit drops with age). Bass: 20–250 Hz. Mid: 250 Hz–4 kHz. Treble: 4–20 kHz. Sample rates: CD audio 44.1 kHz, professional 48 kHz / 96 kHz / 192 kHz. The Nyquist theorem requires sampling at least 2× the highest frequency you want to capture.
- Music tempo: BPM. Common ranges: ballad 60–80 BPM, pop/rock 100–140 BPM, dance 120–135 BPM, drum and bass 160–180 BPM, footwork 160 BPM, speedcore 300+ BPM. Resting heart rate is also reported in BPM (60–100 normal). Metronomes use BPM for music practice.
- Mechanical rotation: rpm. Car engine idle 700–900 rpm, redline 6500–8500 rpm. Washing-machine spin 800–1600 rpm (1400 rpm is standard for European front-loaders). Hard drives 5400 / 7200 / 10 000 / 15 000 rpm. Airliner jet engine: 3000–10 000 rpm at the low-pressure spool. CNC milling spindles 3000–60 000 rpm.
How much is 1 unit of each in hertz?
| Unit | Value in hertz (Hz) |
|---|---|
| 1 Hz (Hertz) | 1 Pa |
| 1 kHz (Kilohertz) | 1000 Pa |
| 1 MHz (Megahertz) | 1000000 Pa |
| 1 GHz (Gigahertz) | 1000000000 Pa |
| 1 THz (Terahertz) | 1000000000000 Pa |
| 1 mHz (Millihertz) | 0.001 Pa |
| 1 rpm (Revolutions per minute) | 0.016666666666666666 Pa |
| 1 BPM (Beats per minute (music)) | 0.016666666666666666 Pa |
| 1 rad/s (Radian per second) | 0.15915494309189535 Pa |
Frequently asked questions about frequency units
How do I convert between any two frequency units?
Multiply by the source unit's hertz-factor and divide by the target's. Example: convert 7200 rpm to Hz → 7200 × (1/60) ÷ 1 = 120 Hz. Or 1 GHz to MHz → 1 × 10⁹ ÷ 10⁶ = 1000 MHz. The converter above does this in real time.
Why is FM radio specifically 87.5 to 108 MHz?
ITU Region 1 (Europe, Africa, Russia, Middle East) and Region 2 (Americas) use 87.5–108 MHz for analog FM broadcasting; Region 3 mostly follows. Japan is the exception with 76–95 MHz. The band sits high enough to require small antennas and avoid daytime ionospheric distortion, low enough that buildings and terrain don't block too much. Stations are spaced 100 or 200 kHz apart depending on country.
What is the difference between Hz and rpm?
They measure the same thing — periodic events per unit time — using different time units. 1 Hz = 1 cycle per second; 1 rpm = 1 cycle per minute. So 1 Hz = 60 rpm and 1 rpm = 1/60 Hz ≈ 0.0167 Hz. Engineers use Hz for electrical/electronic systems and rpm for mechanical rotation because rpm gives more comfortable numbers for shafts.
Is BPM the same as rpm?
Numerically yes — both equal 1/60 Hz. They differ only in cultural context. BPM is used for music tempo and heart rate; rpm for rotating machinery. So 120 BPM (a common pop tempo) = 120 rpm = 2 Hz. A musician would never call their tempo '120 rpm' even though it's mathematically identical.
What is angular frequency (rad/s) and when do I need it?
Angular frequency ω = 2πf radians per second. It is the natural variable in trigonometry — sin(ωt) is cleaner than sin(2πft). Use it in: physics formulas (simple harmonic motion ω² = k/m), AC circuit analysis (impedance jωL, 1/(jωC)), control theory (transfer functions G(jω)), and rotational dynamics (kinetic energy ½Iω²). Convert to ordinary frequency by dividing by 2π.
Why do CPU GHz numbers stop growing?
Power dissipation scales roughly as P ∝ f × V². Pushing clocks higher requires higher voltage, which makes power explode. Around 4–5 GHz, silicon hits a thermal wall on air or simple liquid cooling. Manufacturers responded by adding cores and improving instructions per clock instead. So a 'fast' modern CPU at 5 GHz isn't much faster per core than a 2008 Intel Core 2 Extreme at 3.3 GHz, but it has 16 cores instead of 4.
What's the difference between refresh rate (Hz) and frame rate (fps)?
Refresh rate is how often the monitor redraws its image (in Hz). Frame rate is how many distinct frames per second the GPU produces (in fps). They can differ: a 144 Hz monitor showing a game running at 60 fps duplicates each frame. Variable Refresh Rate (G-Sync, FreeSync) lets the monitor refresh in step with the GPU to avoid tearing and stutter.
What is the difference between mains 50 Hz and 60 Hz?
Both work — there is no clear technical winner. 60 Hz allows slightly smaller transformers and motors run slightly faster. 50 Hz uses slightly less material in long-distance transmission lines. Both are far below human-perceptible flicker for incandescent lighting (faster than ~30 Hz). Synchronous motors (clocks, simple AC) run at speeds proportional to mains frequency, so plugging a 60 Hz device into 50 Hz mains makes it run 17% slow, and vice versa.
How precise are these conversion factors?
All factors are exact by definition. 1 kHz = 1000 Hz, 1 rpm = 1/60 Hz, 1 rad/s = 1/(2π) Hz. The hertz itself is defined by the SI second, which is defined by the cesium-133 atomic transition (9 192 631 770 Hz). The display rounds to ten significant digits.
Can I link to a specific conversion?
Yes. The URL updates as you change units and values, so you can copy the address bar after any conversion. Example: ?from=GHz&to=MHz&x=2.4.
References
Dedicated converter pages
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