Torque is a rotational moment
Torque combines a force with a perpendicular distance from a pivot. That is why torque units include both a force unit and a distance unit, such as N·m or lb-ft.
N·m to lb-ft
One newton-meter is approximately 0.7375621493 pound-feet. Multiply N·m by that factor to estimate lb-ft. In the opposite direction, one lb-ft is approximately 1.3558179483 N·m.
Example
A torque specification of 100 N·m is about 73.76 lb-ft. Keep enough decimal precision for engineering work, then round only at the end according to the required specification.
Do not confuse force and torque
Newtons and pound-force are force units; N·m and lb-ft are torque units. They should not be converted directly without the distance component.
Use the Torque Converter for N·m, lb-ft, lb-in and kgf·m.