What Is Torque, and How Do You Convert Between Its Units?
Torque is twisting force: a force applied at a distance from a pivot. That is why its units are always a force paired with a length. The Torque Converter handles newton-metres, foot-pounds and inch-pounds.
Why the units are pairs
Push on a spanner with ten newtons of force, half a metre from the bolt, and you apply five newton-metres of torque. Double the length of the spanner and you double the torque for the same effort, which is why a longer spanner loosens a tight bolt and why the unit has to mention both.
A newton-metre is the SI unit. A foot-pound is a pound of force at one foot - about 1.356 Nm. An inch-pound is a twelfth of that, around 0.113 Nm, and is the unit for small fasteners. A kilogram-force metre, written kgf·m, is about 9.81 Nm and appears in older Japanese and European manuals.
The quick arithmetic: foot-pounds to newton-metres, multiply by 1.36. Newton-metres to foot-pounds, divide by 1.36 or multiply by 0.74.
The one that gets misread
Foot-pounds of torque and foot-pounds of energy are different quantities with the same name. Torque is force times a perpendicular distance; energy is force times the distance moved. They happen to multiply out to the same units and they are not interchangeable.
Convention tries to separate them - lb-ft for torque, ft-lb for energy - but almost nobody observes it, so you have to read the context. A tightening specification is torque. A muzzle energy or an impact figure is energy. The Energy Converter is the right tool for the second.
Why a torque wrench matters
Fasteners are specified by torque because that is how the tension in the bolt is controlled. Too little and it works loose; too much and the thread strips or the bolt stretches past its elastic limit and will fail later, not now.
Wheel nuts are the case worth caring about: typically 100 to 140 Nm, which is far more than it feels like by hand and far less than a power tool will happily deliver. Overtightened wheel nuts warp brake discs, and the damage shows up weeks later as a vibration nobody connects to the tyre change.
A spark plug is around 25 Nm. A bicycle's carbon seat post clamp might be 5 Nm, which is genuinely easy to exceed with a short Allen key - and the Power Converter is where the related engine figures live, since torque and power describe different things.
Common questions
How many Nm in a foot-pound?
1.356. Multiply by 1.36 and nobody will notice the difference.
Is torque the same as power?
No. Torque is twisting force; power is the rate of work, which is torque times rotational speed.
What does kgf·m mean?
Kilogram-force metre, about 9.81 Nm, from older manuals.
Why specify torque at all?
Because it is a measurable proxy for the tension in the fastener, which is the thing that actually matters and cannot be seen.
Got a torque figure to convert?