Torque Unit Converter

About the Torque Unit Converter

Convert torque — the turning effect of a force, also called moment of force — between newton metres (mN·m, N·mm, N·cm, N·m, kN·m), the kilogram-force units of older specifications and servo datasheets (gf·cm, kgf·cm, kgf·m), the pound-force units of US and UK manuals (ozf·in, lbf·in or in-lb, lbf·ft or ft-lb, kip·in, kip·ft) and the CGS dyne centimetre. Type in either box and the other updates; the table underneath gives the value in every unit.

The factors are exact, worked from standard gravity (9.80665 m/s²), the international pound (0.45359237 kg) and the inch (0.0254 m): 1 lbf·ft is exactly 1.3558179483314004 N·m and 1 kgf·m exactly 9.80665 N·m. Torque from a force on a lever turns a force and a lever arm into a torque — or type 80 kg at 0.4 m in Quick convert — and Common values is a conversion chart of round values in five units. This is a unit converter: it gives no tightening values, which come from the maker of the bolt, wheel or machine.

Common uses

• Setting a torque wrench from a manual written in another unit system.
• Comparing motor, servo and stepper datasheets in N·cm, mN·m, oz-in and kg-cm.
• Car and motorcycle engine torque in N·m, lb-ft and kgf·m.
• Structural bending moments in kN·m, kip·ft and kip·in.
• Physics homework: torque from a force and a lever arm.

Torque and energy share N·m, but they are different

Torque is a force multiplied by its distance from an axis, measured at right angles; energy (work) is a force multiplied by the distance it moves along its own direction. Both come out in newton metres, but they are different quantities, and the SI Brochure (section 2.3.4) is explicit: even though torque has the same dimension as energy, the joule is never used for expressing torque. The two meet in turning work: a torque of 1 N·m acting through an angle of 1 radian does 1 J of work, so one full turn at 10 N·m does 2π × 10 ≈ 62.83 J.

For the same reason this page does not convert torque into joules, kilowatt-hours or calories; energy has its own Energy Converter. In US usage both lbf·ft (lb-ft) and ft·lbf (ft-lb) appear for torque; they are the same size, a pound-force at one foot.

Kilogram-force and pound-force units

• A kilogram-force is the weight of 1 kg under standard gravity, exactly 9.80665 N, so 1 kgf·m = 9.80665 N·m and 1 kgf·cm = 0.0980665 N·m. Datasheets that print “kg·cm” or “kg-cm” mean kgf·cm.
• A pound-force is 0.45359237 kg × 9.80665 m/s² = 4.4482216152605 N exactly, so 1 lbf·ft = 1.3558179483314004 N·m and 1 lbf·in = 0.1129848290276167 N·m; 12 lbf·in make 1 lbf·ft.
• An ounce-force inch is 1/16 lbf·in ≈ 0.00706155 N·m, and a kip is 1,000 lbf.
• mN·m and N·mm are the same size, a thousandth of a newton metre.

Where the factors come from

• NIST SP 811, Appendix B: kgf·m = 9.80665 N·m and dyn·cm = 10⁻⁷ N·m exactly; lbf·ft ≈ 1.355818 N·m, lbf·in ≈ 0.1129848 N·m and ozf·in ≈ 0.007061552 N·m.
• The pound-force is exactly 4.4482216152605 N under standard gravity (NIST SP 811 footnotes); standard gravity is 9.80665 m/s² (3rd CGPM). From these this page derives every factor exactly.

Limitations

• A unit converter only: it gives no tightening torques. Use the value your bolt, wheel or machine manufacturer specifies.
• The lever calculation assumes the force acts at right angles to the arm; at another angle θ the torque is F × r × sin θ, which is less.
• Torque and energy are not converted into each other.
• Results are exact fractions shown to 10 significant digits (marked ≈ when rounded).

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