Use this electronics calculation for a first-pass component, converter, signal, motor, or sensor estimate when the stated operating conditions and units match the device data.

Speed (rpm)

Shaft speed in revolutions per minute.

Kv (rpm/V)

Motor velocity constant in rpm per volt.

Compute the back EMF of a brushless motor in volts as shaft speed divided by its Kv constant in rpm per volt. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Back EMF (V)

Back EMF generated by the spinning motor.

• Motor constants, current, torque, speed, reactive power, and propeller thrust depend on winding temperature, controller, supply sag, losses, saturation, load curve, airflow, and operating point. Nameplate constants and ideal propeller laws need test data for final sizing.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check the result against the current datasheet and worst-case operating corners, then verify the circuit or measurement with simulation and bench testing where failure matters.

• Brushless Motor Kv To Kt

  Convert a brushless motor speed constant in RPM per volt to ideal torque constant in newton-meters per ampere using 60/(2πKv); winding and measurement conventions must match.

• Stepper Motor Pulse Frequency From Rpm

  Convert stepper motor shaft speed to pulse frequency from full or microsteps per revolution; the step count must include the chosen microstepping mode.

• Motor Starting Current

  Estimate DC motor current at startup as applied armature voltage divided by winding resistance, before back EMF develops; drive current limiting is excluded.