Torque Calculator
Choose a lever or an engine. Give the force and the arm length, or give two of power, speed and torque, and get the result.
For the power case, fill in two of power, speed and torque.
Worked examples
Spanner
200 N at 0.3 m, 90 degrees
60 N m
200 x 0.3.
Engine
100 kW at 3,000 rpm
318.3 N m
100,000 / (3000 x 2 x pi / 60).
About Torque Calculator
Torque is the turning effect of a force. For a spanner or a lever it is the force multiplied by the distance from the pivot, and by the sine of the angle between them, so a force at right angles gives the most turning effect. The unit is the newton metre. A 200 newton push at the end of a 0.3 metre spanner gives 60 newton metres. This calculator also handles the engine case, where torque and power are linked through the speed of the shaft.
Power equals torque multiplied by angular speed, where the speed in radians per second is the revolutions per minute times 2 pi over 60. A motor delivering 100 kilowatts at 3,000 rpm provides about 318 newton metres. Use the power mode to find the power from torque and speed, the torque from power and speed, or the speed from power and torque. Results are given in newton metres and pound-force feet, and power in horsepower as well.
How to use Torque Calculator
- Choose the lever mode for a force and arm, or the power mode for a shaft.
- In lever mode, enter the force, the distance from the pivot and the angle.
- In power mode, fill in two of power, speed in rpm and torque.
- Read the torque or the missing value in your chosen units.
Common uses
- Setting a wheel nut or bolt to the correct torque
- Comparing the torque and power of engines and motors
- Choosing a spanner length for a stiff bolt
- Sizing a motor for a given load and speed
Frequently asked questions
What is the torque formula?
Torque = force x distance x sine of the angle between them. At 90 degrees the sine is 1, so it is simply force times distance.
How are torque and power related?
Power = torque x angular speed. In rpm, power in watts is torque in newton metres times rpm times 2 pi over 60.
What is a pound-force foot?
It is the imperial unit of torque: one pound-force acting at one foot. One pound-force foot is 1.3558 newton metres.
Why does a longer spanner help?
The same torque needs less force when the arm is longer. Doubling the arm halves the force you need.