One newton-metre is 0.7375621493 pound-feet. This is the conversion every torque wrench needs, and the unit order matters: torque is written pound-foot, while the energy unit built from the same two quantities is written foot-pound.
About the units
Torque is a force applied at a perpendicular distance from an axis of rotation. A newton-metre is one newton acting one metre from the axis; a pound-foot is one pound-force acting one foot from it. Dimensionally torque and energy are identical — both are force times distance — but they are different physical quantities. Energy is a scalar you can add up; torque is a vector quantity about an axis. The convention of writing lbf·ft for torque and ft·lbf for energy exists specifically to keep them apart on a page, and it is worth respecting even though the arithmetic does not care.
The exact factor
The exact value is 1 lbf·ft = 1.3558179483314004 N·m, from the pound-force of 4.4482216152605 N times the foot of 0.3048 m. Inverted, a newton-metre is 0.737562149277265 pound-feet. Reference points from vehicle work: wheel nuts are typically 110 to 140 N·m, which is 81 to 103 lbf·ft; a spark plug is 25 to 30 N·m or 18 to 22 lbf·ft; and a family car engine produces 200 to 400 N·m, which is 148 to 295 lbf·ft.
Where you meet this conversion
Fastener tightening above all. Torque wrenches are sold marked in one unit or the other, and a European service manual specifying 90 N·m against an American wrench reading in pound-feet needs the conversion before anything is tightened. Under-torquing lets a joint loosen; over-torquing stretches or snaps the fastener, and on an aluminium component it strips the thread. Engine output figures are quoted in both, so comparing a European specification to an American road test requires it. Electric motors, gearboxes and winches are all rated in torque.