Convert Torque from Pound-feet to Newton-meters (lbf-ft to Nm)

Pound-foot to Newton-meter Conversion Formula

To convert torque from pound-feet (lbf·ft) to newton-meters (N·m), multiply by 1.355818.

• N·m = lbf·ft × 1.355818

Step-by-Step Example

A US service manual calls for 85 lbf·ft on a cylinder head bolt, and your torque wrench is graduated in newton-meters:

1. Take the value in pound-feet: 85 lbf·ft
2. Multiply by the factor: 85 × 1.355818 = 115.24
3. Set the wrench to 115 N·m

Where You Need It

• Servicing US vehicles with metric tools — the most common case by far.
• Reading American engine specifications, which quote peak torque in lbf·ft, into metric datasheets.
• Working from older US machinery manuals in a metric workshop.

Check Whether It Is Feet or Inches

US specifications use both lbf·ft and lbf·in, and the difference is a factor of twelve. Small fasteners — electrical terminals, instrument screws, plastic housings — are usually specified in pound-inches. If a figure looks implausibly small for a pound-foot value, it is almost certainly pound-inches; multiply by 0.112985 instead to reach newton-meters.

A Sense of Scale

A rough field check: add a third — 90 lbf·ft is about 120 N·m.

How many pound-feet are in one newton-meter? One Newton-meter (Nm) contains 0.73756212116965551424 Pound-feet (lbf-ft) — the inverse of the factor above. Multiplying by 1.355818 takes you from pound-feet to newton-meters; multiplying by 0.73756212116965551424 brings you back.

Put in words: one pound-foot equals 1.355818 newton-meters, so the pound-foot is the larger unit of this pair. Converting between them never changes the amount of torque being measured — only the size of the unit you count it in.

What Is a Pound-foot (lbf·ft)?

A pound-foot (lbf·ft) is the US customary unit of torque: the twisting effect of one pound-force applied at a perpendicular distance of one foot from the axis.

• 1 lbf·ft = 1.355818 N·m

Pound-foot Versus Foot-pound

You will see both spellings, and in practice they are used interchangeably for torque. Strictly:

• Pound-foot (lbf·ft) is the correct name for torque.
• Foot-pound (ft·lb) properly describes energy — the same distinction as newton-meter versus joule.

Almost every workshop manual, torque wrench and specification sheet writes "ft-lb" and means torque. Read it as pound-foot and you will not go wrong.

Where Pound-foot Is Used

• US automotive service — wheel nuts, cylinder heads, suspension bolts.
• Engine specifications — American engines are advertised in horsepower and lbf·ft.
• Construction and heavy equipment in US markets.
• Torque wrenches sold in the United States, usually graduated in lbf·ft with a secondary N·m scale.

Everyday Reference Points

• A typical car wheel nut: 80–100 lbf·ft.
• A car oil drain plug: 25–30 lbf·ft.
• A large pickup truck engine: 400–1,000 lbf·ft.

Converting Pound-foot

What Is a Newton-meter (N·m)?

A newton-meter (N·m) is the SI unit of torque — the twisting force that makes something rotate. One newton-meter is produced when a force of one newton acts at a perpendicular distance of one metre from the axis of rotation.

• Torque = force × distance, so 1 N·m = 1 N × 1 m

Torque Is Force Times Leverage

The distance matters as much as the force. Pushing on a spanner with 20 N at 0.5 m from the bolt gives 10 N·m. The same 20 N applied through a spanner twice as long gives 20 N·m — identical effort, double the turning effect. This is why a breaker bar loosens a bolt that a short wrench cannot.

The distance is always measured perpendicular to the line of the force. Pulling at an angle reduces the effective lever arm and therefore the torque.

A Newton-meter Is Not a Joule

Both work out to the same base units (kg·m²/s²), but they describe different things and must never be interchanged:

• A joule is energy — a force acting along a distance.
• A newton-meter is torque — a force acting at a distance, perpendicular to it.

Standards keep them apart deliberately: energy is written in J, torque in N·m.

Where Newton-meters Are Used

• Fastener specifications — nearly every modern torque figure is given in N·m.
• Engines and motors — output torque curves, alongside power in kW.
• Power tools — cordless drills and impact drivers are rated in N·m.
• Bicycles — carbon components carry N·m limits because overtightening cracks them.

Quick Reference

Pound-foot to Newton-meter Conversion Table

Here are some quick reference conversions from Pound-foot (lbf-ft) to Newton-meter (Nm):