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Ft-lbs to N·m torque converter (in-lb, kgf·m, kgf·cm, ozf·in)

Type a torque and pick its unit to see it in all six units at once. One foot-pound-force is 1.355818 N·m and one N·m is 0.7376 ft-lb, so 100 ft-lb is 135.58 N·m.

By the Torque Reference editors 3 sources cited Last reviewed Method
Contents6 sections

ft-lb100.00
in-lb1,200.0
N·m135.58
kgf·m13.826
kgf·cm1,382.6
ozf·in19,200

Key takeaways

  • 1 ft-lb = 1.355818 N·m and 1 in-lb = 0.1129848 N·m, from NIST SP 811 Appendix B ⁠1.
  • 1 kgf·m = 9.80665 N·m exactly, because standard gravity is defined as 9.80665 m/s² ⁠1.
  • 1 ft-lb = 12 in-lb exactly. Mixing the two is a twelve-fold error.
  • When a manual prints both units, use the printed number for the unit your wrench reads instead of converting.

Quick facts

1 ft-lb1.355818 N·m = 12 in-lb
1 N·m0.737562 ft-lb = 8.85075 in-lb
1 kgf·m9.80665 N·m = 7.233 ft-lb
1 kgf·cm0.0980665 N·m
1 ozf·in0.007061552 N·m

How it works

The converter turns whatever you type into N·m first, then divides by each unit’s factor. All the factors come from NIST Special Publication 811, Appendix B.8 ⁠1:

Conversion factors used (to N·m)
Unit Multiply by Notes
Pound-force foot (ft-lb, lbf·ft) 1.355818 NIST B.8
Pound-force inch (in-lb, lbf·in) 0.1129848 NIST B.8
Ounce-force inch (ozf·in) 0.007061552 NIST B.8
Kilogram-force meter (kgf·m) 9.80665 exact
Kilogram-force centimeter (kgf·cm) 0.0980665 exact, kgf·m ÷ 100
Newton meter (N·m) 1 SI unit

The kilogram-force units are exact: NIST defines 1 kgf as 9.80665 N, the force of one kilogram under standard gravity (9.80665 m/s²). The inch-pound factors are rounded to seven significant figures in NIST’s table, which is far finer than any torque wrench can read.

Results show ft-lb and N·m to two decimals, in-lb and kgf·cm to one, kgf·m to three and ozf·in to whole numbers.

Worked example

A service manual lists 10 kgf·m and your wrench reads ft-lb.

  • To N·m: 10 × 9.80665 = 98.07 N·m.
  • To ft-lb: 98.0665 ÷ 1.355818 = 72.33 ft-lb.
  • To in-lb: 98.0665 ÷ 0.1129848 = 868.0 in-lb.

Two more you will meet often:

  • 25 N·m on an in-lb wrench: 25 ÷ 0.1129848 = 221.3 in-lb (18.44 ft-lb).
  • 100 ft-lb on a metric wrench: 100 × 1.355818 = 135.58 N·m.

Reading the result

The converter gives exact arithmetic. Manuals usually round. Hyundai prints a spark plug range as 14.7 to 24.5 N·m, 1.5 to 2.5 kgf·m and 10.9 to 18.0 lb-ft ⁠2. Converting 2.5 kgf·m gives 18.08 lb-ft, so the printed 18.0 is rounded down. That is normal and harmless at this precision.

What matters is the unit on the wrench. A click wrench is only as fine as its scale divisions, so there is no point dialing 72.33 on a wrench marked in 1 ft-lb steps: set 72.

Common mistakes

  • Converting a number the manufacturer already printed in both units. Ford prints the F-150 wheel nut torque as 150 lb.ft (204 Nm) ⁠3. Converting 150 ft-lb gives 203.4 N·m. The manual’s own 204 N·m is the spec for a metric wrench, so use it.
  • Swapping in-lb and ft-lb. 89 in-lb is about 10 N·m. 89 ft-lb is about 121 N·m. Small fasteners such as valve covers and M6 bolts are often specified in in-lb, and a ft-lb setting snaps them.
  • Reading kgf·cm as kgf·m. Small-tool specs from Asian makers are often in kgf·cm. 100 kgf·cm is 1 kgf·m, or 9.81 N·m.
  • Confusing torque with force. N·m and ft-lb are torque (force times distance). Newtons, lbf and kN are force: use the clamp load calculator to go from torque to bolt tension, not this converter.
  • Rounding twice. Convert once from the original printed value. Converting a converted number, then rounding again, drifts by a unit or two.

The same factors run every chart on this site: see the methodology.

Sources

  1. 1
  2. 2
  3. 3

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