How to use the foot pounds to newton meters converter
- Enter a value in either the Foot-pounds or Newton-meters field.
- The other field updates automatically with the converted torque.
- Use the result rows below for a formatted readout you can copy.
How the conversion works
A foot-pound (more precisely, a pound-force foot or lbf·ft) is the torque created by one pound of force acting at a perpendicular distance of one foot from a pivot. A Newton-meter is the SI equivalent: one Newton of force at one meter.
The exact relationship comes from two defined constants: one pound-force equals 4.4482216152605 Newtons, and one foot equals exactly 0.3048 meters. Multiplying them gives the conversion factor:
1 ft·lbf = 0.3048 m × 4.4482216152605 N = 1.3558179483314004 N·m
To go from foot pounds to nm, multiply by 1.3558179483314004. To reverse the calculation, divide by that same number (or multiply by 0.737562149).
Common torque values reference
This table shows frequently used torque specifications converted between both units. Values are rounded to three decimal places for readability.
| Foot-pounds (ft·lbf) | Newton-meters (N·m) | Typical use |
|---|---|---|
| 5 | 6.779 | Small electronics screws |
| 10 | 13.558 | Bicycle stem bolts |
| 25 | 33.895 | Spark plugs (many cars) |
| 50 | 67.791 | Suspension components |
| 80 | 108.465 | Passenger car lug nuts |
| 100 | 135.582 | Heavy-duty truck lugs |
| 150 | 203.373 | Crankshaft pulley bolts |
| 250 | 338.954 | Diesel engine flywheel |
Where this conversion matters
Automotive repair manuals published in the United States typically list fastener torques in foot-pounds, while European and Asian manufacturers specify Newton-meters. If you own a torque wrench calibrated in only one unit, you need an accurate foot pounds to nm conversion before tightening critical fasteners like cylinder head bolts or wheel lugs.
Beyond cars, bicycle mechanics frequently encounter mixed units. Shimano and SRAM often publish specs in Nm, while some older American references use inch-pounds or foot-pounds. Industrial maintenance, aerospace assembly, and HVAC work also require switching between imperial and metric torque standards.
Common mistakes to avoid
The most frequent error is confusing foot-pounds of torque (lbf·ft) with foot-pounds of energy (ft·lbf). Although they share the same dimensions, torque is a vector cross product while energy is a scalar dot product. In practice the numerical conversion factor to Newton-meters is identical, but the physical meaning differs.
Another mistake is mixing up inch-pounds and foot-pounds. One foot-pound equals 12 inch-pounds. If a manual calls for 120 inch-pounds and you set your wrench to 120 foot-pounds, you will apply ten times the intended force. Always verify whether the specification reads "in-lb" or "ft-lb" before converting.
Finally, rounding too early introduces errors. When stacking multiple conversions, keep full precision until the final step. This tool uses the exact factor 1.3558179483314004 internally to prevent drift.
Worked examples
Each result below was produced by the same code the tool runs, so you can check your own numbers against them.
| Example | Input | Result |
|---|---|---|
| Car lug nuts (80 ft-lbs) | Foot-pounds (ft·lbf): 80 | Newton-meters: 108.465436; Foot-pounds: 80 |
| Bicycle crank bolt (40 Nm) | Newton-meters (N·m): 40 | Foot-pounds: 29.502486; Newton-meters: 40 |
| Engine torque spec (250 ft-lbs) | Foot-pounds (ft·lbf): 250 | Newton-meters: 338.954487; Foot-pounds: 250 |
| Small fastener (5 Nm) | Newton-meters (N·m): 5 | Foot-pounds: 3.687811; Newton-meters: 5 |
FAQ
What is the exact formula for foot pounds to nm?
Multiply the foot-pound value by 1.3558179483314004. This factor comes from multiplying 0.3048 meters per foot by 4.4482216152605 Newtons per pound-force.
How do I convert Nm back to ft-lbs?
Divide the Newton-meter value by 1.3558179483314004, or multiply by approximately 0.737562. For example, 100 Nm equals about 73.756 ft-lbs.
Is there a difference between lb-ft and ft-lb?
In automotive usage they mean the same thing: pound-feet of torque. Strictly speaking, SAE standard J1995 prefers "lbf·ft" to denote pound-force feet, but "ft-lb" remains common on consumer torque wrenches.
Why does my torque wrench have both scales?
Many modern wrenches print dual scales so mechanics working on imported vehicles do not need to calculate foot pounds to nm manually. The printed numbers should match the 1.3558 ratio.
Can I use this for inch-pounds?
No. Inch-pounds are one-twelfth of a foot-pound. Divide your inch-pound value by 12 first, then use this converter to get Newton-meters.
Does temperature affect torque readings?
Temperature changes the friction coefficient of threads and the elasticity of the wrench spring, but it does not change the mathematical conversion factor between units.