RPM to Hz Converter

Convert revolutions per minute to hertz and hertz to rpm instantly

Conversion Formula

RPM to Hz:

Hz = RPM ÷ 60

To convert revolutions per minute to hertz, divide the rpm value by 60. This is because one hertz equals one cycle per second, whilst one minute contains 60 seconds.

Hz to RPM:

RPM = Hz × 60

To convert hertz to revolutions per minute, multiply the hz value by 60. This converts cycles per second into cycles per minute.

Example Conversion:

Converting 3000 RPM to Hz:

Hz = 3000 ÷ 60 = 50 Hz

A motor rotating at 3000 revolutions per minute has a frequency of 50 hertz.

Step-by-Step Conversion Process

Converting RPM to Hertz:

  1. Identify the rpm value you want to convert (e.g. 1800 rpm)
  2. Divide this value by 60 (since there are 60 seconds in one minute)
  3. The result is your frequency in hertz (1800 ÷ 60 = 30 Hz)
  4. Verify your result makes sense: higher rpm should give higher Hz

Converting Hertz to RPM:

  1. Identify the hertz value you want to convert (e.g. 25 Hz)
  2. Multiply this value by 60 (to convert seconds to minutes)
  3. The result is your rotational speed in rpm (25 × 60 = 1500 rpm)
  4. Double-check: lower Hz values produce lower rpm values

RPM to Hz Conversion Table

Revolutions Per Minute (RPM) Hertz (Hz) Revolutions Per Minute (RPM) Hertz (Hz)
1 rpm0.01667 Hz60 rpm1 Hz
5 rpm0.08333 Hz120 rpm2 Hz
10 rpm0.16667 Hz180 rpm3 Hz
15 rpm0.25 Hz300 rpm5 Hz
20 rpm0.33333 Hz600 rpm10 Hz
25 rpm0.41667 Hz900 rpm15 Hz
30 rpm0.5 Hz1200 rpm20 Hz
40 rpm0.66667 Hz1500 rpm25 Hz
50 rpm0.83333 Hz1800 rpm30 Hz
100 rpm1.66667 Hz3000 rpm50 Hz
500 rpm8.33333 Hz3600 rpm60 Hz
1000 rpm16.66667 Hz6000 rpm100 Hz

Common Motor Speeds and Frequencies

Application Typical RPM Frequency (Hz)
UK Mains Frequency (50 Hz synchronous motor, 2-pole)3000 rpm50 Hz
UK Mains Frequency (50 Hz synchronous motor, 4-pole)1500 rpm50 Hz
Washing Machine Spin Cycle1200-1600 rpm20-26.67 Hz
Car Engine at Motorway Speed2000-3000 rpm33.33-50 Hz
Ceiling Fan (Low Speed)100-150 rpm1.67-2.5 Hz
Ceiling Fan (High Speed)250-350 rpm4.17-5.83 Hz
Industrial Mixer60-600 rpm1-10 Hz
Computer Hard Drive5400-7200 rpm90-120 Hz

Rotational Speed vs Frequency

Rotational speed (rpm) and frequency (Hz) are intrinsically linked but measure different aspects of periodic motion. RPM quantifies how many complete rotations occur in one minute, making it particularly suitable for mechanical systems such as motors, engines, and rotating machinery.

Hertz measures frequency in cycles per second, which is the standard unit in physics and electrical engineering. For rotating systems, one complete rotation equals one cycle. The relationship between these units arises from the time conversion: since one minute equals 60 seconds, dividing rpm by 60 converts revolutions per minute to revolutions per second (hertz).

Why Both Units Matter:

Engineers and technicians frequently work with both units because different contexts favour different measurements. Mechanical engineers typically specify motor speeds in rpm because it directly relates to shaft rotation and mechanical output. Electrical engineers prefer hertz when dealing with AC power supplies, vibration analysis, and control systems, as it aligns with electrical frequency standards.

In the UK, mains electricity operates at 50 Hz. A 2-pole synchronous motor connected to this supply rotates at 3000 rpm, whilst a 4-pole motor runs at 1500 rpm. This demonstrates the direct relationship between electrical frequency and mechanical rotation.

Practical Examples

Example 1: Electric Motor Speed

Question: An electric motor runs at 1440 rpm. What is its frequency in hertz?

Solution:

Hz = 1440 ÷ 60 = 24 Hz

This motor operates at 24 hertz, which suggests it’s likely an induction motor running slightly below synchronous speed on a 50 Hz supply.

Example 2: Vibration Analysis

Question: A vibration sensor detects a frequency of 8.5 Hz. What is this in rpm?

Solution:

RPM = 8.5 × 60 = 510 rpm

The vibration corresponds to 510 revolutions per minute, which might indicate an imbalance in a rotating component.

Example 3: Car Engine Speed

Question: A car engine running at 2400 rpm produces vibrations at what frequency?

Solution:

Hz = 2400 ÷ 60 = 40 Hz

The engine produces vibrations at 40 hertz, which is within the range of human perception and may be felt by passengers.

Frequently Asked Questions

What is the difference between rpm and hertz?
RPM (revolutions per minute) measures rotational speed over one minute, whilst hertz (Hz) measures frequency in cycles per second. They both describe periodic motion but use different time scales. One hertz equals 60 rpm.
How do you convert 60 Hz to rpm?
Multiply the hertz value by 60. For 60 Hz: 60 × 60 = 3600 rpm. This is the synchronous speed of a 2-pole motor on a 60 Hz power supply.
Why is the conversion factor 60?
The factor 60 comes from the time conversion between seconds and minutes. Hertz measures cycles per second, whilst rpm measures cycles per minute. Since one minute contains 60 seconds, you multiply by 60 to convert Hz to rpm, or divide by 60 to convert rpm to Hz.
What is 3000 rpm in hertz?
3000 rpm equals 50 Hz (3000 ÷ 60 = 50). This is the synchronous speed of a 2-pole motor on a 50 Hz supply, which is the standard mains frequency in the UK and much of Europe.
Can you convert any rotational speed to frequency?
Yes, any rotational speed can be converted to frequency. The conversion applies to any rotating system, from slow-turning windmills (a few rpm) to ultra-high-speed turbines (tens of thousands of rpm). The formula remains the same regardless of speed.
Why do UK motors run at different speeds than US motors?
The UK uses 50 Hz mains frequency whilst the US uses 60 Hz. A synchronous motor’s speed depends on the supply frequency and number of poles. A 2-pole motor runs at 3000 rpm on 50 Hz (UK) but 3600 rpm on 60 Hz (US). A 4-pole motor runs at 1500 rpm (UK) versus 1800 rpm (US).
What is synchronous speed?
Synchronous speed is the rotational speed of a motor’s magnetic field, determined by the supply frequency and number of poles. It equals (120 × frequency in Hz) ÷ number of poles. For example, a 4-pole motor on 50 Hz has a synchronous speed of 1500 rpm. Actual motor speed is typically slightly lower due to slip.
How does frequency affect motor speed?
In AC motors, frequency directly controls speed. Higher frequency produces faster rotation, whilst lower frequency slows the motor. Variable frequency drives (VFDs) exploit this relationship to control motor speed by varying the supply frequency. Doubling the frequency doubles the synchronous speed.

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