Frequency converter

Convert rpm to Hz, Hz to rpm, BPM to Hz, GHz to MHz and hertz to radians per second (ω = 2πf), from Hz to THz.

Drafted with AI writing toolsUpdated Checked examples: 4

A number in the “from” unit, or with its own unit
Try
Converted value
Hz
Converted value: 50 Hz
Significant figures: 12; Nearest, ties away from zero
Conversion
3,000 rpm = 50 Hz
Conversion factor
0.0166666666667
Exactness
Exact

3,000 rpm is exactly 50 Hz. One revolution per minute is about 0.01666667 Hz.

The same amount counted in each unit

rpm3,000 rpmHz50 Hz
3,000 rpm in every Frequency unit Rows: 8
UnitValueDefinition
hertz (Hz)50Base unit
kilohertz (kHz)0.051 kHz = 1,000 Hz, exact
megahertz (MHz)0.000051 MHz = 1,000,000 Hz, exact
gigahertz (GHz)5 × 10⁻⁸1 GHz = 1,000,000,000 Hz, exact
terahertz (THz)5 × 10⁻¹¹1 THz = 1,000,000,000,000 Hz, exact
revolution per minute (rpm)3,0001 rpm = 1/60 Hz, exact
beat per minute (BPM)3,0001 BPM = 1/60 Hz, exact
radian per second (rad/s)314.15931 rad/s = 1/(2π) Hz, exact
How it's calculated S
  1. Convert revolution per minute to hertz

    3,000 rpm×160 Hzrpm=50 Hz3{,}000\ \text{rpm} \times \tfrac{1}{60}\ \tfrac{\text{Hz}}{\text{rpm}} = 50\ \text{Hz}

    1 rpm = 1/60 Hz, exact

    Both units are defined exactly and the converted mathematical value has a terminating decimal. A displayed result may still be rounded.

About the frequency converter

One hertz is one cycle per second, so revolutions per minute and beats per minute divide by 60 to give hertz, and the SI prefixes step by 1,000 from kHz to THz. Angular frequency in radians per second is ω = 2πf, so 1 Hz is 6.2832 rad/s; conversions to or from rad/s involve π and are shown to 12 significant figures.

The default converts 3,000 rpm to 50 Hz, the speed of a two-pole motor on a 50 Hz supply. Musicians convert tempo the same way (120 BPM is 2 Hz), and radio users move between MHz and GHz: 2.4 GHz Wi-Fi is 2,400 MHz.

Rpm and BPM count whole cycles per minute, while rad/s counts the angle swept per second. A cycle is 2π radians, so 60 rpm is 1 Hz and 6.2832 rad/s.

How to convert rpm to Hz

Divide revolutions per minute by 60: 3,000 rpm = 50 Hz, because a hertz is one cycle per second and a minute has 60 seconds. Multiply Hz by 60 to get rpm. The same rule turns a tempo or heart rate in beats per minute into hertz: 120 BPM is 2 Hz.

  • 1,800 rpm = 30 Hz
  • 3,000 rpm = 50 Hz
  • 3,600 rpm = 60 Hz
  • 7,200 rpm = 120 Hz, a common hard-drive spindle speed

How to convert Hz to rad/s

Multiply by 2π, about 6.283185: ω = 2πf. So 1 Hz is 6.283185 rad/s and 50 Hz is 314.16 rad/s. A hertz counts whole cycles, a radian per second counts the angle swept, and one cycle is 2π radians.

rpm to rad/s

Combine the two steps: multiply rpm by 2π/60, which is π/30 or 0.104720. So 60 rpm is 6.283185 rad/s, 1,000 rpm is 104.72 rad/s, and 1 rad/s is 9.549297 rpm. Rotation formulas such as power = torque × ω need rad/s.

kHz, MHz and GHz

SI prefixes step by 1,000: 1 GHz = 1,000 MHz = 1,000,000 kHz = 10⁹ Hz. Wi-Fi's 2.4 GHz band is 2,400 MHz, and a 3.5 GHz processor clock ticks 3.5 billion times a second.

Frequency prefixes are always decimal, never the 1,024 used for some memory sizes (NIST SP 811, chapter 4 lists the hertz and the SI prefixes).

Motor speed and mains frequency

A synchronous AC motor turns at 120 × f ÷ p rpm, where p is the number of poles. A two-pole motor runs at 3,000 rpm on 50 Hz mains and 3,600 rpm on 60 Hz; a four-pole motor at 1,500 or 1,800 rpm.

Induction motors run a few percent below that synchronous speed, for example about 2,900 rpm on 50 Hz, which is 48.33 Hz of shaft rotation.

Frequency conversion chart

Repeating decimals and results involving π are rounded to six places.

ValueFromToConverted rate
3000rpmHz50
120BPMHz2
2.4GHzMHz2400
1Hzrad/s6.283185
60rpmrad/s6.283185
1rad/srpm9.549297

Period: the reciprocal of frequency

The period of one cycle is T = 1/f. A 50 Hz supply has a 20 ms cycle, 60 Hz a 16.67 ms cycle, and a beat at 120 BPM lasts 0.5 s.

Common mistakes

  • Putting Hz where rad/s belongs. 10 rad/s is 1.59 Hz, not 10 Hz; the factor between them is 2π.
  • Forgetting the 60. 1,800 rpm is 30 Hz, not 1,800 Hz.
  • Using 1,024 for frequency prefixes. 1 GHz is exactly 1,000 MHz.

The wavelength, frequency and photon energy calculator turns a frequency into a wavelength with c = fλ. The circular motion calculator handles rpm, rad/s and period for rotating objects, and the angle converter converts radians to degrees.

Worked examples

3000 rpm in Hz

Value
3000 rpm
From
revolution per minute (rpm)
To
hertz (Hz)
Converted value
50 Hz

Checked against: 3000 / 60 = 50

120 BPM in Hz

Value
120 BPM
From
beat per minute (BPM)
To
hertz (Hz)
Converted value
2 Hz

Checked against: 120 / 60 = 2

1 Hz in rad/s

Value
1 Hz
From
hertz (Hz)
To
radian per second (rad/s)
Converted value
6.2831853072 rad/s
Exactness
Exact definitions, involves π

Checked against: ω = 2πf = 6.28318530717958647…

2.4 GHz in MHz

Value
2.4 GHz
From
gigahertz (GHz)
To
megahertz (MHz)
Converted value
2,400 MHz

Checked against: 2.4 × 1000

Questions

How do I convert rpm to Hz?

Divide by 60, because hertz counts cycles per second and rpm cycles per minute. 3,000 rpm is 50 Hz, 1,800 rpm is 30 Hz, and 7,200 rpm, a common hard-drive speed, is 120 Hz. To go from Hz to rpm, multiply by 60.

Why does a motor run at 3,000 or 3,600 rpm?

Because its speed is locked to the supply frequency. A synchronous motor turns at 120 × f ÷ p rpm, where p is the number of poles, so a two-pole motor runs at 3,000 rpm on 50 Hz mains and 3,600 rpm on 60 Hz. Induction motors run a few percent below this synchronous speed, for example 2,900 rpm on 50 Hz.

How do I convert Hz to rad/s?

Multiply by 2π, about 6.28319: ω = 2πf. 50 Hz is 314.16 rad/s and 1 Hz is 6.2832 rad/s. Both units reduce to “per second”, but a hertz counts whole cycles while a radian per second counts the angle swept, and one cycle is 2π radians.

How many Hz is 120 BPM?

2 Hz: 120 beats ÷ 60 seconds. Tempo in beats per minute converts to hertz by dividing by 60, so 90 BPM is 1.5 Hz. The same arithmetic applies to heart rate: the American Heart Association gives a usual resting range of 60 to 100 beats per minute for most adults, corresponding to 1 to approximately 1.67 Hz.

How many MHz are in a GHz?

1,000. The shown GHz/MHz/kHz unit steps are factors of 1,000: 1 GHz = 1,000 MHz = 1,000,000 kHz = 10⁹ Hz. Wi-Fi's 2.4 GHz band is 2,400 MHz, and a 3.5 GHz processor clock ticks 3.5 billion times a second. Frequency prefixes are always decimal, never the binary 1,024 used for some memory sizes.

About this calculator

xto=xfrom×ffromftof=one unit expressed in Hz\begin{gathered} x_{\text{to}} = x_{\text{from}} \times \dfrac{f_{\text{from}}}{f_{\text{to}}} \\ f = \text{one unit expressed in } \text{Hz} \end{gathered}

Sources

  1. NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors
  2. NIST Handbook 44, Appendix C — General tables of units of measurement

Checked against references

This calculator includes 4 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.

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