Torque units: overview and conversion factors
Newton-metre, pound-force foot, kgf·m – automotive, engineering and tools
Torque (also called moment or turning force) describes the rotational force of a force acting around a pivot point. It is the product of force and the perpendicular distance to the pivot: M = F × r. The SI unit of torque is the newton-metre (Nm). One Nm corresponds to the torque produced by a force of 1 newton acting at a distance of 1 metre from the pivot point. A longer wrench produces more torque than a shorter one for the same hand force – the lever principle in practice.
In the automotive sector, torque is one of the most important engine specifications. It describes how strongly an engine "pulls", independent of engine speed. High torque means good pulling power, especially when accelerating from a standstill or overtaking. Diesel engines typically have higher maximum torque than comparable petrol engines and reach it at lower engine speeds. Electric motors even develop their maximum torque from zero RPM – an important advantage over combustion engines.
In the English-speaking world, torque is given in pound-force foot (lbf·ft, often abbreviated as "lb-ft" or "ft-lbs"). One lbf·ft is the torque produced by a force of 1 pound-force at a distance of 1 foot: 1 lbf·ft = 4.448222 N × 0.3048 m = 1.355818 Nm. If you are reading American vehicle or tool specifications, you need to convert lbf·ft to Nm. A torque wrench reading of 100 ft-lbs corresponds to about 135.6 Nm.
The kilogram-force metre (kgf·m) is an outdated unit that used to be common in German-speaking and European mechanical engineering: 1 kgf·m = 9.80665 Nm. The unit is intuitive – the torque of a 1 kg mass hanging 1 metre from the pivot point. Older manuals, car instructions and bolt-torque tables still use kgf·m. When working with old machinery or historical documents, converting to Nm is essential.
When it comes to bolt tightening torque, using the correct unit is critical. Too little torque and the bolted joint comes loose; too much and the bolt shears or the thread is damaged. Vehicle manufacturers specify 80–170 Nm for wheel bolts. Cylinder head bolts are tightened to 20–100 Nm, often in several stages with an angle-tightening step. Fine threads need less tightening torque than coarse threads of the same size. Our converter helps you correctly apply manufacturer specifications from different regions.