Nm vs lb-ft vs ft-lb: What's the Actual Difference?

Short answer: ft-lb and lb-ft are the same unit, just written in a different order. Nm (Newton-meter) is a different unit entirely, from the metric system instead of imperial, and the two aren't numerically equal, they need to be converted.

If you've seen a torque spec written both ways and wondered whether someone made a typo, they didn't. Here's what each term actually means.

Ft-lb vs lb-ft: no difference at all

"Foot-pound" and "pound-foot" describe the same unit of torque: one pound of force applied at a distance of one foot from the pivot point. Some manufacturers and regions write it as ft-lb, others as lb-ft. It's a style choice, not a technical one. If you see a spec that says "35 lb-ft" and another that says "35 ft-lb," they mean the same torque value.

The order does technically distinguish two different physical quantities in strict engineering notation (ft-lb for torque; lb-ft is sometimes reserved to avoid confusion with foot-pounds of energy), but in everyday automotive and DIY use, the two terms are used interchangeably, and you don't need to worry about the distinction.

Nm vs ft-lb: this is where it actually matters

Newton-meters (Nm) measure torque using the metric system: one Newton of force applied at a distance of one meter. Since a meter is a lot longer than a foot, and a Newton is a different unit of force than a pound, 1 Nm is not equal to 1 ft-lb.

The actual conversion is:

1 Nm = 0.7375621493 ft-lb

Or going the other way:

1 ft-lb = 1.3558179483 Nm

This matters because most vehicles manufactured outside the US, and increasingly many that are, list torque specs in Nm. If you're working from a manual that gives you Nm figures but your torque wrench is calibrated in ft-lb (or the reverse), using the wrong number without converting can under-tighten or over-tighten a fastener.

Quick reference table

For any value not listed here, use the Nm to ft-lb converter at the top of this site; it handles any number instantly.

Why this confuses people

A few reasons this trips people up:

• Torque wrenches are usually calibrated in one unit only. If your wrench reads ft-lb but your service manual lists Nm, you can't just read the Nm number off the manual and dial it into the wrench; you have to convert it first.

• Nm and ft-lb numbers look deceptively close for small values. 10 Nm and 7.38 ft-lb aren't that far apart visually, so it's easy to eyeball it and assume "close enough." For critical fasteners (head bolts, wheel lugs, suspension components), that gap matters.

• Some spec sheets list both units side by side, which is helpful, but plenty don't, especially older manuals or parts imported from a single-unit region.

The safe rule

If a spec is given in Nm and your wrench only reads ft-lb, always convert before tightening; don't estimate. For anything structural (wheels, suspension, engine mounts, head bolts), a wrong torque value by even 15-20% can mean a fastener that loosens over time or one that's over-stressed and prone to failure.

FAQ

Is Nm bigger or smaller than ft-lb?

Nm is the smaller unit. It takes about 1.36 Nm to equal 1 ft-lb, so a torque spec given in Nm will always be a smaller number than the same torque given in ft-lb.

Are ft-lb and lb-ft ever actually different?

In casual and most professional automotive use, no, they're the same measurement. Some technical standards define lb-ft narrowly to avoid confusion with the unrelated unit "foot-pounds of energy," but for torque wrench and fastener specs, treat them as identical.

Why do some manuals list torque in both Nm and ft-lb?

Manufacturers that sell in both metric and imperial-standard markets often list both so mechanics anywhere in the world can use whichever unit their tools are calibrated in, without needing to convert manually.

For a deeper breakdown of Nm and ft-lb specifically, including a full reference table and real-world torque examples, see our complete Nm to ft-lb guide.