How to convert torque units
Torque is force times distance, so every torque unit pairs a force with a length: newtons and metres (N·m), pounds-force and feet or inches (lbf·ft, lbf·in), kilograms-force and metres or centimetres (kgf·m, kgf·cm). Converting means swapping both parts.
| From | To N·m, multiply by |
|---|---|
| lbf·ft (ft·lb) | 1.35582 |
| lbf·in (in·lb) | 0.112985 |
| ozf·in | 0.00706155 |
| kgf·m | 9.80665 |
| kgf·cm | 0.0980665 |
The factors come from exact definitions: 1 lbf = 4.4482216152605 N, 1 ft = 0.3048 m, 1 in = 0.0254 m, and 1 kgf = 9.80665 N (standard gravity). To go the other way, divide by the same factor.
Worked example
The calculator starts at 100 N·m, a very common tightening value on machines:
- In ft·lb: 100 ÷ 1.35582 = 73.7562 ft·lb
- In in·lb: 73.7562 × 12 = 885.075 in·lb
- In kgf·m: 100 ÷ 9.80665 = 10.1972 kgf·m
The conversion chart above lists the most used values from N·m to ft·lb, ft·lb to N·m and in·lb to N·m, so you can read them without typing.
Common mistakes
- Mixing ft·lb and in·lb. A twelve times error. Small wrenches are usually in in·lb or N·m, big ones in ft·lb.
- kgf·m vs kgf·cm on equipment from Asia or Latin America: a hundred times apart.
- Rounding 1.35582 to 1.4 on a tight spec. The 3% error can push you out of tolerance.
- Treating torque as the goal. What holds the joint is clamp force, and that depends on thread friction. A lubricated thread at the same torque clamps harder than a dry one.
Working with compressed air or hydraulics too? Use the pressure converter for psi, bar and kPa and the flow rate converter for GPM and m³/h.