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Motor Speed – How to Calculate the Gear Motor Rpm

Jiaming CaiFebruary 22, 2024

Definition: Motor speed (Motor Rpm) is a measure that describes the number of revolutions of the motor shaft per minute – RPM (Revolutions Per Minute). Motor speed is one of the key parameters to measure the working status of the motor.

In the application of geared motors, the concept of speed is particularly important. The gear motor reduces the original speed of the motor through a reduction mechanism while increasing the torque of the output shaft. Accurate calculation of the speed after deceleration can ensure that the motor outputs the desired operating performance.

Effect of Motor Speed :

FeatureEffect of Rotation Speed
Output TorqueThe output torque of the motor is inversely proportional to the rotational speed. The higher the speed, the lower the torque.
Control PrecisionThe stability of the motor speed directly affects the operating accuracy of the control system.
Motor LifeThe higher the motor speed, the greater the motor wear and the shorter the motor life.
Noise and VibrationThe higher the motor speed, the greater the motor vibration and noise.
Attention : The above comparison and analysis are mainly applicable to the performance of the same motor model at different operating speeds.

Basic Concepts of Motor Speed

1. Rated Speed

The rated speed represents the speed that the motor can output at its highest efficiency point. This parameter is determined by the motor manufacturer when designing and testing the motor and represents the average speed at which the motor can operate safely and efficiently under the standard operating conditions for which it was designed.

2. No-Load Speed

The no-load speed refers to the speed when the motor is running without load.

3. Stall Speed

The Stall speed represents the maximum torque that the motor can withstand. At this time, the motor speed is 0 and the torque reaches the maximum.

When selecting a motor and designing a system, it is very important to consider the these speed of the motor because it affects the matching between the motor and the drive equipment, the control strategy, and the final application efficiency. Proper matching ensures that the motor operates at its optimal efficiency point while meeting the power and speed requirements required by the application.

How to Calculate the Gear Motor Rpm

The gear motor is composed of a motor and a gear structure. To calculate the speed of the gear motor, we need to understand two concepts, the motor speed and the gear ratio.

  • Motor Speed: The speed of the motor refers to the speed of the motor without a reduction structure, that is, the rated speed of the motor.
  • Gear Ratio:The gear ratio is an inherent characteristic of the gearbox design and is expressed as the ratio of the input speed to the output speed.


DC-36555 Motor 12V6000 rpm No-Load speed :6000 Rated Speed: 5100

Gear ratio: 1:99.5K

Gear motor rpm = 5400 / 99.5= 51rpm

PG36555126000-99.5K – PDF →

51rpm is the rated rpm of gear motor. It means the gear motor can output a speed of 51rpm and a torque of 2.25N.m at the maximum efficiency point.

Based on the test report, we can see the speed of the gear motor has a dynamic range, and the speed will vary dynamically depending on the load of the motor.

Based on this model : PG36555126000-99.5k Let’s take a look at a comparison of speeds under different torque conditions.

It can be seen from the figure that as the torque increases, the rotational speed decreases linearly. This shows that within the range of the data you provided, the motor speed decreases when it is subjected to more torque.

Motor Speed Calculator

Motor Speed Calculator

Base Speed (RPM):

Reduction Ratio:

Final Speed (RPM):

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