Physics overview
What is torque?
Torque measures the turning effect of a force around a pivot or axis. Greater force or a longer lever arm produces greater torque.
Formula
Torque formula
Torqueτ = Fr
- τ is torque in newton-meters.
- F is perpendicular force in newtons.
- r is lever-arm distance in meters.
Worked example
An 80 N force acts 0.5 m from a pivot
- Write the formula: τ = Fr.
- Substitute the values: τ = 80 × 0.5.
- Calculate the torque: τ = 40 N·m.
Force direction
Perpendicular force assumption
This calculator uses τ = Fr, which assumes the force acts perpendicular to the lever arm. For a force at an angle, the general formula is τ = Fr sin θ.
Rearranged equations
Solve for force or lever arm
Force
F = τ ÷ r
Divide torque by lever-arm distance.
Lever Arm
r = τ ÷ F
Divide torque by force.
Units
Standard SI units
Use newton-meters for torque, newtons for force, and meters for the lever arm.
Real-world applications
Where torque calculations are used
- Wrenches, spanners, and fasteners.
- Doors, levers, and rotating handles.
- Motors, shafts, and mechanical systems.
- Laboratory rotational-equilibrium experiments.
Calculation limits
Important assumptions
- Torque, force, and lever arm must be greater than zero.
- Force is assumed to act perpendicular to the lever arm.
- Lever arm means perpendicular distance from the pivot.
- The calculator uses magnitudes and does not represent rotation direction.
- Units are not converted automatically.
Related tools
Continue your mechanics calculations
Use the Force Calculator to solve force, mass, or acceleration.
Use the Work Calculator to calculate work, force, or distance.
Questions and answers
Torque calculator FAQ
What formula does the torque calculator use?
It uses τ = Fr for a force acting perpendicular to the lever arm, where torque equals force multiplied by perpendicular distance.
What is the SI unit of torque?
The SI unit of torque is the newton-meter, written as N·m.
What is the lever arm in a torque calculation?
The lever arm is the perpendicular distance from the pivot or axis of rotation to the line of action of the force.
How do you calculate force from torque?
Divide torque by the lever-arm distance using F = τ ÷ r.