Torque Units

Torque describes the turning effect of a force about a point or axis. The SI unit is the newton metre (N·m). Torque-unit conversions change the unit used to express the same torque; they do not change the force or lever arm that produced it.

Torque formula

For position vector r and force F, torque is τ = r × F. Its magnitude is |τ| = rF sin θ = F r⊥, where θ is the angle between r and F and r⊥ is the perpendicular lever arm.

Common torque units

Common units include N·m, kilonewton metres (kN·m), pound-force feet (lbf·ft), pound-force inches (lbf·in), ounce-force inches (ozf·in), and kilogram-force metres (kgf·m). The pound-force foot may also be written ft·lbf, pound-force inch as in·lbf, and ounce-force inch as in·ozf. The symbols lbf and ozf mean force, not mass.

NIST lists 1 lbf·ft = 1.355818 N·m and 1 ozf·in = 0.007061552 N·m. For example, 10 lbf·ft = 13.55818 N·m.