How to Calculate Torque
What is Torque?
Torque (τ) is a rotational force — the tendency of a force to rotate an object about an axis. It equals force × distance × sin(angle). Engineers use it for tightening bolts, designing engines, and analysing structures.
Formula
τ = r × F × sin(θ) | τ = F × d (perpendicular distance)
- τ
- Torque (N⋅m or lb-ft)
- r
- Lever Arm Length (m or ft)
- F
- Applied Force (N or lb)
Step-by-Step Guide
- 1τ = F × d × sin(θ)
- 2F = applied force (Newtons)
- 3d = distance from pivot to force application (metres)
- 4θ = angle between force and lever arm
- 5Maximum torque occurs at θ = 90°
Worked Examples
Input
50 N force, 0.3 m wrench, 90°
Result
15 N·m torque
Input
Same force at 45°
Result
10.6 N·m — 29% less due to angle
Frequently Asked Questions
Why is angle important in torque?
Only the perpendicular component of force creates torque. Force applied parallel to the lever arm creates zero torque.
How does lever arm length affect torque?
Torque increases linearly with lever arm length. A longer wrench provides more torque with the same force — why leverage works.
What is the difference between torque and force?
Force is a push or pull. Torque is rotational force, measured at a distance from a pivot point. Torque depends on both force and distance.
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