Torque Calculator
Calculate torque, force, or lever arm length using the formula τ = r × F. Select the calculation mode below.
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What is Torque?
Torque (also called moment or moment of force) is a measure of the tendency of a force to rotate an object about an axis. It is the rotational equivalent of linear force. The formula is:
τ = r × F
Where τ (tau) is torque, r is the lever arm distance from the axis of rotation, and F is the applied force. The SI unit of torque is the newton-meter (N·m). Torque is a vector quantity that follows the right-hand rule for direction.
In everyday life, torque is experienced when turning a door handle, using a wrench, pedaling a bicycle, or any action involving rotation. The longer the lever arm, the greater the torque produced by the same force — which is why long-handled wrenches make it easier to loosen tight bolts.
Common Torque Reference Values
| Application | Torque (N·m) |
|---|---|
| Tightening a spark plug | 15 |
| Tightening a lug nut | 135 |
| Tightening an engine head bolt | 88 |
| Bicycle pedal crank (typical) | 35 |
| Opening a jar lid (typical) | 5 |
| Door handle torque | 0.5 |
| Electric screwdriver max | 5 |
| Car wheel center nut | 400 |
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Authoritative References
Frequently Asked Questions
What is torque?
Torque is a measure of the rotational force applied to an object around an axis. It is calculated as the product of force and the perpendicular distance from the axis of rotation (lever arm). The formula is τ = r × F, where τ is torque, r is the radius or lever arm length, and F is the applied force. Torque is a vector quantity, meaning it has both magnitude and direction.
How do I calculate torque?
Torque is calculated by multiplying the applied force by the perpendicular distance from the axis of rotation: τ = r × F × sin(θ). When the force is applied perpendicular to the lever arm (θ = 90°), sin(θ) = 1, so τ = r × F. For example, applying a 50 N force at the end of a 0.3 m wrench produces 15 N·m of torque.
What is the difference between torque and force?
Force is a push or pull that causes linear motion, while torque causes rotational motion. Force is measured in newtons (N), while torque is measured in newton-meters (N·m). A force applied at a distance from a pivot point creates torque. The same force can produce different torques depending on the lever arm length.
What are common torque units?
The SI unit is the newton-meter (N·m). Other common units include pound-foot (lb·ft), pound-inch (lb·in), kilogram-meter (kg·m), and dyne-centimeter (dyne·cm). In the automotive industry, lb·ft is commonly used in the US, while N·m is standard elsewhere.
How does lever arm length affect torque?
Torque is directly proportional to lever arm length. A longer wrench produces more torque with the same applied force. This is why mechanics use longer breaker bars for stubborn bolts — doubling the handle length doubles the torque output, making it easier to loosen tight fasteners.
What is the relationship between torque and horsepower?
Horsepower is a measure of power, which is torque multiplied by rotational speed. The formula is: HP = (Torque × RPM) / 5252. This means an engine can produce high horsepower through either high torque or high RPM. The 5252 constant comes from unit conversions between lb·ft, RPM, and horsepower.