Newton-metres to pound-inches (N·m to lbf·in)

The formula

lbf·in = N·m × 8.850745791

Where the factor comes from — each unit by its definition, then its size in SI:

• 1 N·m is the SI unit of torque.
• 1 lbf·in = lbf × in = 0.112984829028 N·m

Dividing the two SI sizes gives the factor: 8.85074579133 (rounded for display; the underlying ratio is fixed by the definitions). The reverse factor is 0.112984829028.

Torque is force times lever arm, in newton-metres. Workshop manuals mix N·m, lbf·ft and lbf·in; a torque wrench set in the wrong unit over- or under-tightens by a large factor.

Worked examples

• A car wheel nut: 110 N·m = 973.582 lbf·in — 110 × 8.850745791 = 973.582
• A bolt spec in a US manual (30 lbf·ft): 40.6745 N·m = 360 lbf·in — 40.6745 × 8.850745791 = 360
• A bicycle stem bolt: 10 N·m = 88.5075 lbf·in — 10 × 8.850745791 = 88.5075

Frequently asked questions