Calculate ideal permanent-magnet brushed DC motor stall torque from current and torque constant, or estimate it from compatible voltage, resistance and back-EMF data. The gearbox mode uses an explicit torque-loss factor; running power efficiency alone does not establish blocked-state losses.

Ideal permanent-magnet brushed DC motor model. Stall can overheat a motor or damage a gearbox. Calculated torque is not a continuous rating or a safe stall-test instruction.

Stall Torque Formula

The following ideal current-to-torque formula assumes compatible motor data and neglects motor friction and saturation. Stall torque is not a continuous operating rating; prolonged stall can overheat a motor or damage a gearbox.

Tstall = Is ร— K
  • Where Tstall is the Stall Torque (N-m)
  • Is is the stall current (amps) 
  • K is the motor's torque constant (N-m/amp) 

To calculate stall torque, multiply the stall current by the motor's torque constant.

How to Calculate Stall Torque?

The following two example problems outline how to calculate the Stall Torque.

Example Problem #1:

  1. First, determine the stall current (amps). In this example, the stall current (amps) is measured to be 120.
  2. Next, determine the motor's torque constant (N-m/amp). For this problem, the motor's torque constant (N-m/amp) is calculated to be 50.
  3. Finally, calculate the Stall Torque using the formula above: 

Tstall = Is * K

Inserting the values from above and solving the equation with the imputed values gives: 

Tstall = 120*50 = 6,000 (N-m)

Example Problem #2: 

Using the same process as example problem 1, we first define the variables outlined by the formula. In this case, the values are:

stall current (amps) = 60

motor's torque constant (N-m/amp) = 20

Entering these values yields:

Tstall = 60 * 20 = 1200 (N-m)