The Motor Torque Calculator converts a motor's power and speed into its rotational torque — the twisting force a motor delivers at its shaft. Enter your motor power (in kW or HP) and motor speed (RPM) from the nameplate, then select your preferred torque unit (N·m or ft-lbs) to get the motor torque along with the converted power and angular velocity in rad/s.
Motor Torque
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Power
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Angular Velocity
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Motor torque is calculated using the formula: T = (60 × P × 1000) / (2π × N), where T is torque in N·m, P is power in kW, and N is speed in RPM. This formula relates the motor's rated power and speed to determine its torque output.
Motor torque refers to electric motors and is calculated from electrical power ratings, while engine torque typically refers to internal combustion engines. Both represent rotational force, but electric motors provide constant torque at rated conditions, whereas engines have torque curves that vary with RPM.
A 1 HP motor's torque depends on its speed. At 1800 RPM, a 1 HP motor produces approximately 4.2 N·m (3.1 ft-lbs) of torque. Lower speeds result in higher torque, following the inverse relationship between power, speed, and torque.
Rated torque is the continuous torque a motor can produce at its rated power and speed during normal operation. Starting torque is the torque available when the motor starts from rest, which is typically 1.5-3 times higher than rated torque for most electric motors.
Motor speed (RPM) is inversely related to torque for a given power. At constant power, higher speeds result in lower torque, and lower speeds produce higher torque. This relationship is fundamental to motor selection for specific applications.
Slip is the difference between synchronous speed and actual rotor speed in AC induction motors, expressed as a percentage. Slip allows the motor to produce torque - without slip, there would be no relative motion between the magnetic field and rotor, resulting in zero torque.
To convert torque units: 1 N·m = 0.7376 ft-lbs, and 1 ft-lb = 1.356 N·m. Multiply N·m by 0.7376 to get ft-lbs, or multiply ft-lbs by 1.356 to get N·m. Both units measure rotational force but are used in different engineering standards.
Actual motor torque can be affected by voltage variations, frequency changes, temperature, motor condition, and load characteristics. The calculated rated torque assumes ideal conditions - real-world performance may vary due to these factors and mechanical losses.