Torque Calculator (Force × Lever Arm)
By Santaji GadepatilinUpdated October 27, 2026
Torque is the turning effect of a force — force multiplied by the distance from the pivot. It explains why long spanners loosen tight bolts and how levers multiply force.
How to use the torque calculator
Enter the force, the lever arm length (distance from the pivot to where the force acts) and the angle between them (90° for a push at right angles). The calculator gives the torque. To find the force needed for a given torque, press × on Force.
Torque formula
τ = F × r × sin θ
Torque is greatest when the force is perpendicular to the lever (θ = 90°) and zero when pushing along the lever.
Force needed for common torques
| Torque | 20 cm spanner | 30 cm spanner | 50 cm breaker bar |
|---|---|---|---|
| 25 N·m | 125 N (12.7 kgf) | 83 N (8.5 kgf) | 50 N (5.1 kgf) |
| 50 N·m | 250 N (25.5 kgf) | 167 N (17.0 kgf) | 100 N (10.2 kgf) |
| 100 N·m | 500 N (51.0 kgf) | 333 N (34.0 kgf) | 200 N (20.4 kgf) |
| 150 N·m | 750 N (76.5 kgf) | 500 N (51.0 kgf) | 300 N (30.6 kgf) |
| 250 N·m | 1250 N (127.4 kgf) | 833 N (84.9 kgf) | 500 N (51.0 kgf) |
Levers and balance
A lever balances when torques on both sides are equal: F₁ × r₁ = F₂ × r₂. A 50 kg child 2 m from a see-saw pivot balances a 100 kg adult 1 m from it.
Torque in everyday life
| Task | Typical torque |
|---|---|
| Opening a jar lid | 1–3 N·m |
| Bicycle pedal (hard effort) | 50–100 N·m |
| Car wheel nuts | 80–140 N·m |
| Small car engine (peak) | 100–250 N·m |
Torque wrenches
Use a calibrated torque wrench for bolts with a specified torque. Hold the handle at its marked grip point — pulling elsewhere changes the effective lever length.
Frequently asked questions
What is the torque formula?
τ = F × r × sin θ, where F is the force, r the distance from the pivot and θ the angle between them.
Why is a longer spanner easier to use?
Torque is force × distance. Doubling the handle length halves the force needed for the same torque.
What is the difference between torque and work?
Both use newton-metres, but torque is a turning effect (a vector), while work is energy (a scalar), usually written in joules.
How do I convert N·m to ft-lb?
Multiply by 0.7376. 100 N·m ≈ 73.8 lbf·ft.