Torque, moment, or moment of force (see the terminology below) is the tendency of a force to rotate an object about an axis, fulcrum, or pivot.
It measures how much force a tool has to be able to rotate, like with an impact drill or other tool. Without sufficient torque, some tasks that require more force would be impossible to perform with the tool.
Just as a force is a push or a pull, torque can be considered a twist to an object.
Mathematically, torque is defined as the cross product of the lever-arm distance vector and the force vector, which tends to produce rotation.
Loosely speaking, torque measures the turning force on an object such as a bolt or a flywheel.
For example, pushing or pulling the handle of a wrench connected to a nut or bolt produces a torque (turning force) that loosens or tightens the nut or bolt.
The symbol for torque is typically the Greek letter tau. When it is called the moment of force, it is commonly denoted M.
The magnitude of torque depends on three quantities: the force applied, the length of the lever arm connecting the axis to the point of force application, and the angle between the force vector and the lever arm.
R is the displacement vector (a vector from the point from which torque is measured (typically the axis of rotation) to the point where force is applied), F is the force vector, × denotes the cross product, θ is the angle between the force vector and the lever arm vector.
The length of the lever arm is particularly important; choosing this length appropriately lies behind the operation of levers, pulleys, gears, and most other simple machines involving a mechanical advantage.
The SI unit for torque is the newton metre (N⋅m). For more on the units of torque, see Units.
I'm Joost Nusselder, the founder of Tools Doctor, content marketer, and dad. I love trying out new equipment, and together with my team I've been creating in-depth blog articles since 2016 to help loyal readers with tools & crafting tips.