What Is Torque?
Torque is the rotational equivalent of force, measuring how effectively a force causes an object to rotate around a pivot point. The formula is torque equals distance times force, where distance is the lever arm length from the pivot to the point where force is applied, and force is applied perpendicular to the lever arm. A mechanic in Chicago tightening a bolt with a 0.3-meter wrench applies 80 newtons of force at the handle, producing 24 newton-meters of torque. That same 24 N·m would require only 40 newtons if the wrench were 0.6 meters long, which is why longer wrenches make tightening easier.
Torque is measured in newton-meters (N·m) in the metric system and pound-feet (lb·ft) in the imperial system. One N·m equals approximately 0.7376 lb·ft. For calculating force from mass and acceleration, see our Force Calculator.
What This Calculator Does
This torque calculator solves for any one of the three variables in the torque equation. Select which value you want to find, enter the other two, and the result is calculated instantly with automatic unit conversion between N·m and lb·ft.
- Inputs: Any two of force (N), distance (m), or torque (N·m)
- Outputs: The third value, plus torque in lb·ft and a unit conversion reference
How the Calculation Works
τ = r × F (torque = distance × force)
F = τ / r (force = torque / distance)
r = τ / F (distance = torque / force)
These three formulas are algebraic rearrangements of the same equation. The lever arm distance must be measured from the pivot point to where the force is applied, and the force must be perpendicular to the lever arm for this simple formula to apply. If the force is applied at an angle, only the perpendicular component contributes to torque: τ = r × F × sin(θ). The NIST Guide to SI Units defines the newton-meter and its relationship to other units.
Common Use Cases
Bolt tightening: Calculate the force needed at a given wrench length to achieve a specified torque specification. Engine output: Engine torque ratings describe the rotational force available at the crankshaft. Lever systems: Determine the mechanical advantage of levers and crowbars. For converting torque and RPM to horsepower, see our Horsepower Calculator.
Limitations
This calculator assumes the force is applied perpendicular to the lever arm. If the force is applied at an angle, the actual torque is reduced by the sine of the angle between the force vector and the lever arm. The calculator does not account for friction, which opposes rotation and reduces the effective torque. It also does not handle dynamic torque situations involving angular acceleration, which require the moment of inertia. For speed and distance calculations, see our Speed Calculator.