Torque is rotational force — the tendency of a force to rotate an object about an axis: τ = F × r (force multiplied by perpendicular distance from pivot). The SI unit is the newton-metre (N·m). Car engine torque is quoted in N·m (Europe/metric markets) or pound-feet (ft·lb) in the US, and it directly determines acceleration feel and towing capacity — more torque means stronger pulling power at lower engine speeds.
Do not confuse ft·lb of torque with ft·lb of energy — they share the same dimensions but describe fundamentally different physical quantities (one is rotational, the other is linear work). Proper bolt tightening requires specific torque values: a typical car wheel nut is torqued to 100–140 N·m; cylinder head bolts often require 80–120 N·m. A longer wrench multiplies your effective torque — applying 200 N of force at 0.5 m from the pivot delivers exactly 100 N·m.
| 1 ft·lb | = 1.35582 N·m |
| 1 N·m | = 0.73756 ft·lb |
| 1 kgf·m | = 9.80665 N·m |
| 1 in·lb | = 0.11299 N·m |
| 1 kN·m | = 1,000 N·m |
| 100 ft·lb | = 135.6 N·m |