Classical Mechanics
Torque Calculator
Calculate torque (rotational force), lever arm length, applied force or angle using τ = rFsinθ. Supports Newton-metres, foot-pounds and inch-pounds.
τ = r × F × sinθ
90° = perpendicular force = maximum torque
Examples
Enter values to calculate torque.
What is torque?
Torque is the rotational equivalent of force — it is the tendency of a force to cause rotation about an axis. τ = rFsinθ shows that torque depends on the force magnitude, the perpendicular distance from the axis (lever arm), and the angle between the force and lever arm vectors. Maximum torque occurs at θ = 90° (force perpendicular to lever arm).
This is why longer spanners are easier to use — the same force applied at a greater radius creates more torque. It's also why pushing a door at the hinged side requires much more force than pushing at the outer edge.