RPM to Hz Converter
Convert revolutions per minute to hertz (rpm to Hz) for motors and machines
1 rpm = 0.0166667 Hz, and 60 rpm = 1 Hz. To convert rpm to Hz, divide the revolutions per minute by 60. For example, 1,800 rpm = 30 Hz.
Revolutions per minute to Hertz converter
Live- 0.10471976 rad/s
- 0.0000166667 kHz
- 1.666667e-8 MHz
- 1.666667e-11 GHz
How to convert rpm to hertz
Revolutions per minute count how many complete turns a shaft makes in 60 seconds. Hertz count cycles per second. Since one revolution is one cycle and a minute is exactly 60 seconds, the conversion is a single division: Hz = rpm ÷ 60. A turntable at 45 rpm turns 0.75 times per second, and a 7,200 rpm hard drive platter makes 120 turns per second. For kilohertz, megahertz and radians per second as well, open the frequency converter.
The trap is that hertz describes cycles, not angles. If a formula needs angular velocity, it wants radians per second, and one turn is 2π radians, so rad/s = rpm × 2π ÷ 60 ≈ rpm × 0.10472. For the angle side of that conversion, see the degrees to radians converter. The second trap is electrical: a motor's supply frequency in Hz is usually not its shaft speed, as the table below shows.
Step by step
- Take the rotational speed in revolutions per minute (rpm).
- Divide it by 60, the number of seconds in a minute.
- Read the result in hertz (revolutions per second).
- For angular velocity, multiply the hertz value by 2π to get rad/s.
See it on a scale
Worked examples
A record turntable, a four-pole motor on a 60 Hz supply, and a desktop hard drive.
45 rpm ÷ 60 = 0.75 Hz
= 0.75 Hz
1,800 rpm ÷ 60 = 30 Hz
= 30 Hz
7,200 rpm ÷ 60 = 120 Hz
= 120 Hz
How do you calculate power from torque and rpm?
Power in watts = torque in N·m × rpm × 2π ÷ 60, so an engine making 200 N·m at 3,000 rpm delivers about 62,832 W, or 62.83 kW.
The rpm has to become radians per second first, because power equals torque times angular velocity (P = T × ω). Plugging in hertz, without the 2π, gives an answer about 6.28 times too small.
In US units the constants fold into one number: horsepower = lb-ft × rpm ÷ 5,252. That figure is 33,000 ft·lbf per minute, the definition of one mechanical horsepower, divided by 2π (5,252.11). It is also why torque and horsepower curves cross at 5,252 rpm on any dyno chart plotted in lb-ft and hp.
Switch the result to other units with the kW to hp converter, or change torque units with the N·m to ft-lbs converter.
How do I convert rpm to Hz in Excel or Google Sheets?
With the rpm in cell A2, enter =A2/60 to get hertz; the formula is identical in Google Sheets.
- Hz back to rpm: =A2*60
- rpm to rad/s: =A2*PI()/30, since 2π ÷ 60 simplifies to π ÷ 30
- Seconds per revolution: =60/A2
- Synchronous motor speed: =120*B2/C2, with the supply frequency in B2 and the number of poles in C2
For a column of nameplate speeds, wrap the result in ROUND for tidy output: =ROUND(A2/60,2) turns 1,750 rpm into 29.17 Hz and 3,450 rpm into 57.5 Hz. PI() returns π to 15 significant digits, so the rad/s column is as precise as the data you enter.
If a data logger already records revolutions per second, those values are hertz as they stand and need no conversion at all.
Is 1 Hz the same as one revolution per second?
Yes: for a rotating shaft, 1 Hz means exactly one revolution per second (1 rps), which equals 60 rpm.
Both count complete cycles each second, so the numbers match: 25 Hz, 25 rev/s and 1,500 rpm describe the same speed. The difference is convention. ISO 80000-3 calls this quantity rotational frequency, measured in reciprocal seconds, while the BIPM SI Brochure keeps the special name hertz for periodic phenomena in general. Many engineers therefore write rev/s or r/min on drawings, so nobody mistakes a shaft speed for an electrical frequency.
What 1 Hz is not is 1 rad/s. One revolution sweeps 2π radians, so 1 rev/s is about 6.2832 rad/s. Mixing up the two is the classic source of a 2π error in rotating-machinery calculations.
RPM to Hz conversion chart
Rotational speeds from slow gear drives to high-speed spindles, converted to hertz. Motor nameplate speeds such as 1,750 and 3,450 rpm are included because they come up in pump and fan work.
| Revolutions per minute (rpm) | Hertz (Hz) |
|---|---|
| 1 rpm | 0.0167 Hz |
| 10 rpm | 0.1667 Hz |
| 30 rpm | 0.5 Hz |
| 45 rpm | 0.75 Hz |
| 60 rpm | 1 Hz |
| 78 rpm | 1.3 Hz |
| 100 rpm | 1.6667 Hz |
| 120 rpm | 2 Hz |
| 300 rpm | 5 Hz |
| 500 rpm | 8.3333 Hz |
| 600 rpm | 10 Hz |
| 720 rpm | 12 Hz |
| 750 rpm | 12.5 Hz |
| 900 rpm | 15 Hz |
| 1,000 rpm | 16.6667 Hz |
| 1,200 rpm | 20 Hz |
| 1,440 rpm | 24 Hz |
| 1,500 rpm | 25 Hz |
| 1,750 rpm | 29.1667 Hz |
| 1,800 rpm | 30 Hz |
| 2,400 rpm | 40 Hz |
| 2,880 rpm | 48 Hz |
| 3,000 rpm | 50 Hz |
| 3,450 rpm | 57.5 Hz |
| 3,600 rpm | 60 Hz |
| 5,400 rpm | 90 Hz |
| 6,000 rpm | 100 Hz |
| 7,200 rpm | 120 Hz |
| 9,000 rpm | 150 Hz |
| 10,000 rpm | 166.6667 Hz |
| 12,000 rpm | 200 Hz |
| 15,000 rpm | 250 Hz |
| 20,000 rpm | 333.3333 Hz |
RPM vs hertz: what is the difference?
Revolutions per minute and hertz both count complete cycles, but over different time spans and in different traditions: rpm belongs to machines, hertz to physics and electrical work.
| Attribute | Revolutions per minute | Hertz |
|---|---|---|
| Symbol | rpm | Hz |
| System | Rotational speed | SI derived unit |
| Defined as | 1/60 Hz | 1 cycle per second |
| One unit equals | 0.016666667 Hz | 60 rpm |
| What it measures | Complete turns of a shaft per minute | Complete cycles of any repeating event per second |
| Time base | One minute (60 s) | One second |
| Standard status | Outside the SI; NIST SP 811 lists it as r/min | SI derived unit (s⁻¹) in the BIPM SI Brochure |
| Typical everyday values | 45 rpm singles, 800 rpm engine idle, 7,200 rpm hard drives | 50 or 60 Hz mains, a 120 Hz drive platter, the 440 Hz tuning note |
| Where it is used | Tachometers, motor nameplates, machine tool spindles | Power supplies, drive displays, vibration spectra, acoustics |
4 key differences
- The same rotation always reads 60 times larger in rpm than in Hz, because rpm counts turns per minute and Hz counts them per second.
- Hertz can describe sound, voltage or light as well as rotation, while rpm only ever describes something that turns.
- On an induction motor nameplate the Hz value is the electrical supply and the rpm value is the loaded shaft speed, which sits below synchronous speed because of slip.
- Engine and motor speeds stay in rpm because they give convenient whole numbers, such as 3,600 rpm instead of 60 Hz.
AC motor speeds from supply frequency
An AC induction motor's magnetic field turns at the synchronous speed, rpm = 120 × supply Hz ÷ number of poles. The rotor runs a few percent slower (slip), so a four-pole 60 Hz motor is typically rated about 1,750 rpm and a two-pole one about 3,450 rpm. For wiring and motor installation, follow local electrical code and use a licensed electrician; the electrical calculators cover power and current.
| Poles | 50 Hz supply | Shaft Hz at 50 Hz | 60 Hz supply | Shaft Hz at 60 Hz |
|---|---|---|---|---|
| 2 | 3,000 rpm | 50 Hz | 3,600 rpm | 60 Hz |
| 4 | 1,500 rpm | 25 Hz | 1,800 rpm | 30 Hz |
| 6 | 1,000 rpm | 16.67 Hz | 1,200 rpm | 20 Hz |
| 8 | 750 rpm | 12.5 Hz | 900 rpm | 15 Hz |
| 12 | 500 rpm | 8.33 Hz | 600 rpm | 10 Hz |
Everyday rotation speeds in rpm, Hz and rad/s
The period column is the time for one full revolution (60,000 ÷ rpm milliseconds). Engine and appliance figures are typical values that vary by model; turntable and hard drive speeds are standard.
| Machine | Speed | Hertz | One revolution | Angular velocity |
|---|---|---|---|---|
| Vinyl LP turntable | 33⅓ rpm | 0.5556 Hz | 1,800 ms | 3.49 rad/s |
| 7-inch single turntable | 45 rpm | 0.75 Hz | 1,333.33 ms | 4.71 rad/s |
| Shellac record turntable | 78 rpm | 1.3 Hz | 769.23 ms | 8.17 rad/s |
| Car engine at idle | 800 rpm | 13.3333 Hz | 75 ms | 83.78 rad/s |
| Washing machine spin cycle | 1,200 rpm | 20 Hz | 50 ms | 125.66 rad/s |
| Car engine cruising on a highway | 2,500 rpm | 41.6667 Hz | 24 ms | 261.8 rad/s |
| Laptop hard drive | 5,400 rpm | 90 Hz | 11.11 ms | 565.49 rad/s |
| Car engine near a typical redline | 6,500 rpm | 108.3333 Hz | 9.23 ms | 680.68 rad/s |
| Desktop hard drive | 7,200 rpm | 120 Hz | 8.33 ms | 753.98 rad/s |
| Enterprise hard drive | 10,000 rpm | 166.6667 Hz | 6 ms | 1,047.2 rad/s |
| Fastest enterprise hard drive | 15,000 rpm | 250 Hz | 4 ms | 1,570.8 rad/s |
What units can express rotational speed?
Besides rpm, rotational speed is written in hertz, radians per second, degrees per second or seconds per revolution, and each converts from rpm with one constant:
- Hertz (revolutions per second): rpm ÷ 60.
- Radians per second: rpm × 2π ÷ 60, about rpm × 0.10472.
- Degrees per second: rpm × 360 ÷ 60 = rpm × 6.
- Seconds per revolution: 60 ÷ rpm.
Take a car engine at 3,000 rpm: it turns at 50 Hz, 314.16 rad/s or 18,000 degrees per second, and completes one revolution every 20 ms. The per-minute unit stays popular because it gives convenient whole numbers for engines and motors; per-second units are what physics formulas and data sheets expect. The seconds to minutes converter helps with any other time base.
How is rpm used in vibration analysis?
Analysts divide shaft rpm by 60 to find the 1× running-speed frequency in Hz, because most machine faults show up at that frequency or its multiples. A pump turning at 1,780 rpm, for example, shows its 1× peak at 1,780 ÷ 60 = 29.67 Hz. Imbalance appears mainly at 1×, misalignment often at 2× (59.33 Hz), and looseness at several multiples.
Fans and pumps also produce a blade pass frequency, equal to the shaft speed in Hz times the number of blades or vanes. A 6-blade fan at 1,200 rpm has a blade pass frequency of 1,200 ÷ 60 × 6 = 120 Hz. Some analysts work in cycles per minute (CPM) instead, which equals rpm for 1× and avoids the division altogether. Higher-frequency components are often quoted in kHz; the Hz to kHz converter handles them.
Common rpm to Hz mistakes
- Assuming a 60 Hz motor turns at 60 Hz. Only a two-pole motor comes close (about 3,450 to 3,600 rpm). A four-pole motor on 60 Hz turns near 1,800 rpm, which is 30 Hz at the shaft.
- Reading a drive display as shaft speed. A variable frequency drive shows its electrical output in Hz. The shaft speed depends on the motor's poles and slip.
- Using Hz where rad/s is required. Formulas for torque, power and kinetic energy expect angular velocity. Forgetting the 2π factor makes results about 6.28 times too small.
- Multiplying instead of dividing. Hz is always the smaller number: 1,200 rpm is 20 Hz, not 72,000 Hz.
Every rotation and frequency unit is on the frequency converter.
Sources and further reading
The standards and references behind the numbers on this page. Links open in a new tab.
Standards and official sources
Further reading
- Revolution per minuteWikipedia
- HertzWikipedia
RPM to Hz FAQs
Short, exact answers to what people ask most.
How do you convert rpm to Hz?
Divide the revolutions per minute by 60. For example, 1,500 rpm ÷ 60 = 25 Hz, and 600 rpm = 10 Hz.
What is 3600 rpm in Hz?
3,600 rpm is exactly 60 Hz, or 60 revolutions per second. It is the synchronous speed of a two-pole motor on a 60 Hz supply.
How many Hz is 1 rpm?
1 rpm equals 1/60 Hz, about 0.0166667 Hz. It takes 60 rpm to make 1 Hz.
What rpm does a 50 Hz motor run at?
It depends on the number of poles. A 50 Hz supply gives synchronous speeds of 3,000 rpm with 2 poles, 1,500 rpm with 4 and 1,000 rpm with 6; actual induction motor speeds are a few percent lower.
What is 7200 rpm in Hz?
7,200 rpm is 120 Hz, so a 7,200 rpm hard drive platter completes one revolution every 8.33 milliseconds.
How do I convert rpm to rad/s?
Multiply rpm by 2π and divide by 60, which is about rpm × 0.10472. For example, 1,000 rpm is about 104.72 rad/s.
What is 1000 rpm in Hz?
1,000 rpm is 16.6667 Hz, since 1,000 ÷ 60 = 16.6667. One revolution takes 60 milliseconds.
What is 3000 rpm in Hz?
3,000 rpm equals exactly 50 Hz, the synchronous speed of a two-pole motor on a 50 Hz supply.
How many rpm is 100 Hz?
100 Hz is 6,000 rpm when one cycle is one revolution. Multiply hertz by 60 to get revolutions per minute.
What is 10000 rpm in Hz?
10,000 rpm is 166.6667 Hz. An enterprise hard drive spinning that fast completes a revolution every 6 ms.
Is rpm an SI unit?
No. The revolution per minute is outside the SI, which expresses rotational speed in reciprocal seconds (revolutions per second) or, as angular velocity, in radians per second.
Related conversions
The hertz and radian per second from the BIPM SI Brochure (9th edition); rotational frequency from ISO 80000-3; revolution per minute and the mechanical horsepower (550 ft·lbf/s) from NIST SP 811 (2008); synchronous motor speed from NEMA MG 1. Last updated . How we verify our numbers.