Torque Calculator: Force, Distance and Rotational Effect
Torque is rotational force: the product of the force applied and the perpendicular distance from the pivot. Doubling the length of a spanner doubles the torque for the same effort, which is why lever length is the first thing to change when a fastener will not move.
Units and conversions
- 1 newton metre (N·m) = 0.7376 pound-feet (lb·ft).
- 1 lb·ft = 1.3558 N·m.
- 1 lb·ft = 12 lb·in — a common source of ten-fold errors on small fasteners.
Why the angle matters
Only the component of force perpendicular to the lever produces torque, so the full formula is τ = F × r × sin(θ). Pulling at 90° to the spanner is the most efficient position; at 45° you lose about 29% of the effect, and pulling straight along the handle produces no torque at all.
Tightening fasteners correctly
Manufacturer torque specifications assume a specific thread condition. Lubricated threads reach the same clamping force at a lower torque reading, so applying the dry specification to an oiled bolt can overstretch it. Tighten multi-bolt joints in a star or criss-cross pattern in two or three progressive stages, and re-check after the first heat cycle where the manual says to.
Torque and power
In rotating machinery, power = torque × angular velocity. An engine producing high torque at low rpm pulls strongly from low speeds, while high power at high rpm gives top-end speed. That relationship is why gearboxes exist: gearing trades speed for torque without changing the power available.
Key takeaways — Torque Calculator
- Torque = force × perpendicular distance from the pivot.
- Longer levers multiply torque; angle of pull changes the effective force.
- Follow manufacturer specifications and note whether they assume dry or lubricated threads.