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Motor Torque: Definition, How to Calculate Motor Torque and Torque Applications

Jiaming CaiMarch 7, 2024

Motor torque is a key measure of motor rotational force. Motor torque directly affects the motor’s ability to start, accelerate, and maintain a specific load. Therefore, when designing and selecting a motor, it is very important to understand what is the motor torque.

What is a Motor Torque

From a physical point of view, motor torque is defined as the product of force and moment arm (that is, the vertical distance from the point of force application to the axis of rotation), usually in Newton meters (N·m).

In the field of motors, motor torque can be understood as the rotational effect produced by the motor, which is generated by the interaction of the current and the magnetic field inside the motor.

Starting Torque


Starting Torque refers to the maximum torque that the motor can generate at the moment of starting, that is, when it starts running from a standstill.

In practical applications, the starting torque of the motor must be greater than the minimum load torque of the system at startup to ensure that the motor can start smoothly and accelerate to the rated speed.
Insufficient starting torque may cause the motor to fail to start, or excessive consumption of electrical energy during the starting process, affecting the efficiency and life of the motor.

Rated Torque

The rated torque represents the maximum torque that the motor can continuously output under rated power and rated speed, and is also the working torque of most motors.

Rated torque is an important parameter for motors and gear motors. DONCEN MOTOR will complete basic parameter testing before the motor leaves the factory. Customers can see the rated torque of the motor here.

motor test curve-rated torque
Motor test Cruve-Rated Torque

As shown in the figure, the rated torque is considered to be the torque output at the maximum efficiency point of the motor under load.

Stall Torque

Stall Torque refers to the maximum torque that the motor can generate at 0 speed (i.e., stalled state). In the case of locked rotor, the output shaft of the motor does not rotate, but it tries to overcome the external resistance and generate the maximum rotation torque.

motor test cruve- Stall torque
Motor test Cruve-Stall Torque

The stall torque is considered in the extreme operating environment of the motor.
Attention: The motor cannot operate in the stalled torque range for a long time, otherwise the motor will be easily damaged.

How to Calculate the Motor Torque

The torque of the motor is related to the power of the motor and the speed of the motor.

Motor Torque Calculation Formulas

The formula for calculating motor torque \( T \) (in Newton-meters N·m) is:

\[ T = \frac{60 \times P}{2\pi \times N} \]


  • \( P \) is the motor power in watts (W),
  • \( N \) is the motor speed in revolutions per minute (RPM).


Assuming the power of the motor is 100W and the speed is 100 rpm, we can calculate the torque of the motor:

T = 60 * 100 / (2Π * 100) = 9.55N.m

Motor Torque Calculator

Motor Torque Calculator

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