Enter the voltage and the current across the motor into the calculator to determine the motor winding resistance. This calculator can also determine the motor voltage or current when given the other variables.

Motor Winding Resistance Formula

The following equation is used to calculate the Motor Winding Resistance.

R = V/I 
  • Where R is the motor winding resistance (ohms)
  • V is the voltage (volts)
  • I is the current (amps)

To calculate a motor winding resistance, divide the motor voltage by the motor current.

What is Motor Winding Resistance?


The motor winding resistance is the resistance inherent in the windings of an electrical machine. The higher the winding resistance, the less current will flow through the windings and thus cause less torque to be produced.

For example, if you are driving a machine that requires a maximum of 5 HP but has 8 HP motors available, you can use a 4-HP motor as long as it has a lower winding resistance than the other 8-HP motors. This will result in your machine operating at its maximum torque output of 5 HP, with only half of the required horsepower being used.

Lower winding resistance results in higher efficiency and better performance in general terms. An adequately designed motor should have an appropriate input voltage range, frequency, and whole-load currents for reliable operation over its service life.

To achieve this, it is necessary to know details about the power losses in the machine, including voltage drop in cables and current loss in windings, and other factors that affect performance and efficiency, such as ambient temperature and air circulation within the motor enclosure.

How to Calculate Motor Winding Resistance?

The most important thing in calculating Motor Winding Resistance is determining what type of windings are in use. This can sometimes be tricky as each manufacturer may use different types for their motors. It is also important to make sure that there are no short circuits in the winding, as this will also result in an incorrect calculation.

Once you have determined which type of windings are in your motor, you can begin calculating Motor Winding Resistance by using the following equations:

For slip ring motors: R = ρ L / (3.5 * N * R s )

Where: R = Resistance (Ω)

L = Length of wire (m)

N = Number of turns per coil

R s = Cross-sectional area (m2)

ρ = Resistivity factor of copper