Torque Converter

Torque is a force multiplied by the perpendicular distance from the pivot (τ = F × r). With force in newtons and distance in metres the unit is N·m; with pound-force and feet it is lbf·ft.

result = value × N·m-per-unit(from) ÷ N·m-per-unit(to)

• 1 lbf·ft = 4.4482216152605 N × 0.3048 m = 1.3558179483 N·m (exact)
• 1 N·m = 1 ÷ 1.3558179483 = 0.7375621493 lbf·ft

Both factors come from defined values of the pound-force and the international foot, so the conversion has no measurement uncertainty.

ft-lb, lb-ft and lbf·ft. In the US, torque on wrenches is often labelled ft-lb or lb-ft. Strictly, foot-pound (ft·lbf) is a unit of work/energy and pound-foot is torque, but numerically they are the same and tool makers use them interchangeably. This converter treats them as lbf·ft.

Other units in the menu:

• lbf·in (in-lb): small fasteners, bicycle parts and electronics. 1 lbf·ft = 12 lbf·in, so 60 in-lb = 5 lbf·ft ≈ 6.78 N·m.
• kgf·m: older Japanese and European manuals. 1 kgf·m = 9.80665 N·m.
• N·cm: screwdrivers and small motors. 100 N·cm = 1 N·m.
• ozf·in: small servo motors and RC hobby specs. 16 ozf·in = 1 lbf·in.
• kN·m: structural engineering and large engines. 1 kN·m = 1000 N·m.

Typical specs to sanity-check: a car wheel nut is commonly 100–140 N·m (75–105 lbf·ft); a spark plug 20–30 N·m; a carbon bicycle stem bolt 4–6 N·m. If your converted value for a carbon part reads 50, a unit has gone wrong.

Torque is not the whole story. Bolt clamp force depends on thread friction, lubrication and washer finish; a lubricated bolt torqued to a dry spec can be over-tensioned by 20–30%. Follow the manufacturer's instructions on whether threads should be clean, oiled or thread-locked.

Using a torque wrench extension. If you fit a crow's-foot adapter or extension that lengthens the wrench, the actual torque at the bolt rises. The corrected setting is wrench setting = required torque × L ÷ (L + E), where L is the wrench length and E the extension length along the same line. For a 135 N·m target with a 450 mm wrench and a 50 mm crow's foot, set 135 × 450 ÷ 500 = 121.5 N·m. Convert to lbf·ft afterwards if your wrench is imperial.

Bicycle bolt in inch-pounds

Inputs: 5, From N·m, To lbf·in

A carbon seatpost clamp says 5 N·m, but your small wrench reads in-lb. Enter 5 with N·m → lbf·in: 5 ÷ 0.112984829.

Result: 44.25372896

Set 44 in-lb; over-tightening carbon can crack it.

A US wheel-nut spec in N·m

Inputs: 100, From lbf·ft, To N·m

A manual says 100 ft-lb. Enter 100 with lbf·ft → N·m: 100 × 1.3558179483.

Result: 135.5817948

Set a metric wrench to 136 N·m.

Metric spec on an imperial wrench

Inputs: 120, From N·m, To lbf·ft

A European car lists 120 N·m for its wheel bolts. Enter 120 with N·m → lbf·ft.

Result: 88.50745791

Set the wrench to 89 lbf·ft (or 88 if it only has even steps).

Is ft-lb the same as lb-ft?

For torque settings, yes, numerically. Purists reserve ft·lbf for energy, but wrench makers use both labels.

How do I convert inch-pounds?

Select lbf·in as the From unit. 120 in-lb = 10 lbf·ft ≈ 13.56 N·m.

What about kgf·m in old manuals?

Select kgf·m; the tool multiplies by 9.80665 to get N·m (2 kgf·m = 19.6133 N·m). 10 kgf·m ≈ 98.07 N·m ≈ 72.33 lbf·ft.

Why is the factor so specific?

It is exact: pound-force (4.4482216152605 N) times the international foot (0.3048 m).

How do I get engine power from torque?

P(kW) = τ(N·m) × rpm ÷ 9549. For lbf·ft, hp = τ × rpm ÷ 5252.

My wrench only goes to 80 lbf·ft but the spec is 120 N·m — is that enough?

120 N·m converts to about 88.5 lbf·ft, so an 80 lbf·ft wrench cannot reach it. Use a larger wrench rather than over-cranking past the scale.

Should I round up or down?

Round to the nearest setting your wrench offers. Manufacturer specs usually carry their own tolerance band of ±5–10%.