Electric Motor Torque Calculator
Find motor torque from power and speed.
An electric motor's torque relates to its power output and rotational speed.
How the Math Works
The Electric Motor Torque Calculator uses the fundamental relationship between power, torque, and rotational speed. Torque (T) in Newton-meters equals 9549 multiplied by the motor's power in kilowatts (kW), divided by its rotational speed in revolutions per minute (rpm). The constant 9549 is a conversion factor that accounts for the relationship between power units (watts), angular velocity (radians per second), and the unit conversions needed to express torque in Newton-meters. This formula derives from the basic physics equation Power = Torque × Angular Velocity, rearranged to solve for torque.
Practical Applications
To use this calculator practically, simply input the motor's power rating in kilowatts and its operating speed in rpm. For example, a 15 kW motor running at 1500 rpm produces approximately 95.49 Nm of torque. This calculation is essential for engineers and technicians when selecting motors for specific applications, determining if a motor can handle required loads, or sizing drive systems. Always ensure the motor operates within its rated torque capacity to prevent overheating and mechanical failure.
Day-to-Day Use
Understanding motor torque helps in everyday situations involving electric motors, from household appliances to vehicle systems. When choosing between different power tools, knowing torque helps you select equipment that can handle demanding tasks without stalling. For vehicle maintenance, torque calculations help determine if your car's engine can tow safely or if gear changes are needed for hills. Even in home projects, understanding torque prevents damage to tools and ensures proper performance of electric devices.
Worked example
5 kW at 1500 rpm → about 31.8 N·m.
FAQ
Why more torque at low rpm?
For the same power, torque rises as speed falls (T = P/ω).