Frequency Converter
Convert frequency between Hz, kHz, MHz, GHz, RPM, and BPM, with period and wavelength context for audio, radio, and engineering. How it works
Use the Frequency Converter
About the Frequency Converter
RPM ÷ 60 = Hz, and Hz × 60 = RPM or BPM. So 3,600 RPM is 60 Hz, 45 RPM is 0.75 Hz and 2 Hz is 120 BPM. For the metric units, 1 kHz = 1,000 Hz, 1 MHz = 1,000 kHz and 1 GHz = 1,000 MHz.
RPM and BPM to Hz
| RPM or BPM | Hz | Time per turn or beat | Where you see it |
|---|---|---|---|
| 33⅓ | 0.5556 | 1.8 s | LP record |
| 45 | 0.75 | 1.33 s | 7-inch single |
| 60 | 1 | 1 s | One beat per second |
| 78 | 1.3 | 769.2 ms | 78 RPM record |
| 120 | 2 | 500 ms | Two beats per second |
| 1,500 | 25 | 40 ms | 4-pole motor on a 50 Hz supply |
| 1,800 | 30 | 33.33 ms | 4-pole motor on a 60 Hz supply |
| 3,000 | 50 | 20 ms | 2-pole motor on a 50 Hz supply |
| 3,600 | 60 | 16.67 ms | 2-pole motor on a 60 Hz supply |
| 7,200 | 120 | 8.33 ms | Common hard disk speed |
RPM and BPM share a column because both count events per minute. The motor rows are synchronous speeds, from RPM = 120 × supply Hz ÷ number of poles. Their Hz column is shaft turns per second, which is not the supply frequency.
Hz to RPM and BPM
| Hz | RPM or BPM | Period |
|---|---|---|
| 0.5 Hz | 30 | 2 s |
| 1 Hz | 60 | 1 s |
| 2 Hz | 120 | 500 ms |
| 5 Hz | 300 | 200 ms |
| 10 Hz | 600 | 100 ms |
| 50 Hz | 3,000 | 20 ms |
| 60 Hz | 3,600 | 16.67 ms |
| 100 Hz | 6,000 | 10 ms |
| 400 Hz | 24,000 | 2.5 ms |
| 1,000 Hz (1 kHz) | 60,000 | 1 ms |
Hz, kHz, MHz and GHz
| Unit | Hz | kHz | MHz | GHz |
|---|---|---|---|---|
| 1 Hz | 1 | 0.001 | 0.000001 | 0.000000001 |
| 1 kHz | 1,000 | 1 | 0.001 | 0.000001 |
| 1 MHz | 1,000,000 | 1,000 | 1 | 0.001 |
| 1 GHz | 1,000,000,000 | 1,000,000 | 1,000 | 1 |
| 1 THz | 1,000,000,000,000 | 1,000,000,000 | 1,000,000 | 1,000 |
The converter prints results below 0.001 in scientific notation, so 1 Hz appears as 1.0000e-6 MHz.
Methodology
Every unit is converted to hertz first. RPM and BPM are divided by 60, rad/s by 2π (1 Hz = 6.2832 rad/s) and °/s by 360. kHz, MHz, GHz and THz are multiplied by 1,000 per step, and rev/s and cps are equal to Hz. A period in seconds becomes f = 1 ÷ T. The period readout is 1 ÷ f. Wavelength is c ÷ f with c = 299,792,458 m/s and is left blank for RPM, BPM, rev/s, rad/s and °/s.
How to use this tool
- Type a value and choose its unit: Hz, kHz, MHz, GHz, THz, RPM, rev/s, rad/s, °/s, BPM, cps or a period in seconds.
- Choose the unit to convert to. You can type in either box and the other one updates.
- Under the result, read the period, the nearest musical note for 16 Hz to 20 kHz, and the wavelength and radio band.
Frequently asked questions
- Is RPM the same as BPM?
- As numbers, yes: both count events per minute, so the same divide-by-60 rule turns either into Hz. 1,800 RPM is 30 Hz, 90 BPM is 1.5 Hz, and 50 Hz is 3,000 of either. Only what is counted differs, turns or beats.
- How do I convert rad/s to Hz?
- Divide by 2π, about 6.2832. 100 rad/s is 15.92 Hz, or 954.93 RPM. Going the other way, 1 Hz is 6.2832 rad/s and 360 °/s.
- What is 45 RPM in BPM?
- 45. A record at 45 RPM turns 0.75 times per second, once every 1.33 s. Playing a 33⅓ RPM record at 45 speeds it up by a factor of 1.35, so a 100 BPM track plays at 135 BPM.
- How do I convert between Hz, kHz, MHz and GHz?
- Each step is a factor of 1,000. Divide by 1,000 to move up a unit and multiply to move down: 20,000 Hz = 20 kHz, 98 MHz = 98,000 kHz, 2.4 GHz = 2,400 MHz.
- Does the converter calculate wavelength?
- Yes, as λ = c ÷ f using the speed of light in a vacuum, 299,792,458 m/s. That is the wavelength of a radio or light wave: 98 MHz is 3.06 m and 2.4 GHz is 12.49 cm. For sound in air at 20 °C, divide 343 m/s by the frequency instead, which puts 440 Hz at about 0.78 m.
- How do I convert a period to frequency?
- Divide 1 by the period: f = 1 ÷ T. Pick Period (s) as the unit and type the time for one cycle: 0.02 s is 50 Hz, 0.5 s is 2 Hz or 120 BPM, and 0.001 s is 1 kHz. A period of 0 has no frequency, so the field asks for a number greater than 0.
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