The formula
lbf·ft = N·m × 0.7375621493
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·ft = lbf × ft = 1.35581794833 N·m
Dividing the two SI sizes gives the factor: 0.737562149277 (rounded for display; the underlying ratio is fixed by the definitions). The reverse factor is 1.35581794833.
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 = 81.1318 lbf·ft — 110 × 0.7375621493 = 81.1318
- A bolt spec in a US manual: 40.6745 N·m = 30 lbf·ft — 40.6745 × 0.7375621493 = 30
- A bicycle stem bolt: 10 N·m = 7.37562 lbf·ft — 10 × 0.7375621493 = 7.37562
Frequently asked questions
How many pound-feet is 1 N·m?
1 N·m = 0.737562149277 lbf·ft.
How do I convert pound-feet back to newton-metres?
Divide by 0.737562149277 — or multiply by 1.35581794833: 1 lbf·ft = 1.35581794833 N·m.