Torque Calculator
Calculate torque from force and lever arm, or from power and rotational speed.
About the Torque Calculator
Choose force and lever arm (with the angle the force makes with the arm), or power and speed. The calculator gives torque in newton-metres, pound-feet and kilogram-force metres.
Torque is the turning effect of a force: force × perpendicular distance from the pivot. For a rotating shaft, power = torque × angular speed, so torque = power ÷ (2π × rpm ÷ 60).
The formula
τ = F r sin θ; τ = P ÷ ω
Worked example
Pushing a 0.3 m wrench with 100 N at right angles
- τ = 100 × 0.3 × sin 90° = 30 N·m
- = 22.13 lb·ft
- Pushing at 30° to the handle gives only 15 N·m
Questions people ask
Why does a longer wrench help?
Torque grows with lever length for the same force.
Torque vs power?
Power is torque × speed; high torque at low rpm gives pulling ability.
How do I convert lb·ft to N·m?
Multiply by 1.3558.