Torque units and their equivalents
| Unit | Symbol | In N·m |
|---|---|---|
| Newton-meter | N·m | 1 N·mbase unit |
| Kilonewton-meter | kN·m | 1,000 N·m |
| Kilogram-force meter | kgf·m | 9.80665 N·m |
| Pound-foot | lbf·ft | 1.35582 N·m |
| Pound-inch | lbf·in | 0.112985 N·m |
Frequently asked questions
Is a newton-meter the same as a joule?
No, even though both come out as a newton times a meter. The joule measures work, a force that moves something along its own direction; the newton-meter measures a moment, a force that turns something around a point. They are never added, and no calculation converts one into the other. The International System keeps two names for one dimension precisely so the two are not confused.
How many newton-meters in a kilogram-force meter?
9.80665 exactly, because a kilogram-force is the weight of one kilogram under standard gravity. A tightening spec of 10 kgf·m is therefore 98.07 N·m, and 3 kgf·m is 29.4 N·m. The unit disappeared from European specifications in the 1980s but it still appears on Japanese and Italian service manuals, where it is sometimes written m·kg with the terms reversed.
Is it lb-ft or ft-lb?
Both are written and both mean the same torque. The order that follows the physics is force first, distance second, so lbf·ft, but the trade writes ft-lb just as often. The real thing to watch is not the order but the distance: lbf·in is twelve times smaller than lbf·ft, and a small engine spec given in pound-inches read as pound-feet will shear the bolt.
Does an extension change what my torque wrench reads?
A straight extension in line with the socket changes nothing: the lever arm of the wrench is unchanged. An offset adapter, a crowfoot for instance, does change it, because it adds its own length to the arm. With a wrench of length L and an adapter that extends it by E, set the wrench to the target multiplied by L divided by L plus E. A 400 mm wrench with a 50 mm crowfoot set to 100 N·m therefore delivers 112 N·m at the bolt.
What torque do everyday jobs take?
A car wheel nut is usually near 110 N·m, that is 81 lb-ft; a bicycle stem bolt is 5 N·m, that is 44 lb-in, and this is where pound-inches earn their place. A spark plug sits around 25 N·m and an engine drain plug around 30. These are orders of magnitude and never a substitute for the figure in the manual, which is the only one that accounts for the thread and its lubrication.