Convert Torque from Pound-inches to Pound-feet (lbf-in to lbf-ft)

Pound-inch to Pound-foot Conversion Formula

Example

Let's convert 5 Pound-inch (lbf-in) to Pound-foot (lbf-ft).

Using the formula:

Therefore, 5 Pound-inch (lbf-in) is equal to 0.41666666666666666667 Pound-foot (lbf-ft).

How many pound-inches are in one pound-foot? One Pound-foot (lbf-ft) contains 12 Pound-inches (lbf-in) — the inverse of the factor above. Multiplying by 0.083333333333333333333 takes you from pound-inches to pound-feet; multiplying by 12 brings you back.

Put in words: one pound-inch equals 0.083333333333333333333 pound-feet, so the pound-inch is the smaller 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-inch (lbf·in)?

A pound-inch (lbf·in) is one pound-force applied at one inch from the axis of rotation. It is the small-torque companion to the pound-foot.

• 1 lbf·ft = 12 lbf·in (exactly, since a foot is twelve inches)
• 1 lbf·in = 0.112985 N·m

Why a Smaller Imperial Unit Exists

Many fasteners are tightened to far less than one pound-foot. Writing "0.4 lbf·ft" invites a decimal-point error on a shop floor; writing "5 lbf·in" does not. Small-torque work therefore uses inch units almost exclusively.

Where Pound-inch Is Used

• Electrical terminals — breaker lugs and terminal blocks are specified in lbf·in, and both under- and overtightening cause failures.
• Electronics and instrument assembly — small screws in enclosures and connectors.
• Aerospace fasteners — small-diameter hardware throughout aircraft assembly.
• Optics, firearms and precision equipment — mounting screws where excess torque distorts the assembly.

Torque screwdrivers and small click wrenches are graduated in lbf·in for exactly this range.

A Common and Expensive Mistake

Confusing lbf·in with lbf·ft applies twelve times the intended torque. On a 5 lbf·in electrical terminal this shears the screw or crushes the conductor. Always check which unit the specification uses before setting a wrench.

Converting Pound-inch

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

Pound-inch to Pound-foot Conversion Table

Here are some quick reference conversions from Pound-inch (lbf-in) to Pound-foot (lbf-ft):