Convert Torque from Pound-inches to Ounce-inches (lbf-in to ozf-in)

Pound-inch to Ounce-inch Conversion Formula

Example

Let's convert 5 Pound-inch (lbf-in) to Ounce-inch (ozf-in).

Using the formula:

Therefore, 5 Pound-inch (lbf-in) is equal to 80.000000945833334705 Ounce-inch (ozf-in).

How many pound-inches are in one ounce-inch? One Ounce-inch (ozf-in) contains 0.062499999261067716 Pound-inches (lbf-in) — the inverse of the factor above. Multiplying by 16.000000189166666941 takes you from pound-inches to ounce-inches; multiplying by 0.062499999261067716 brings you back.

Put in words: one pound-inch equals 16.000000189166666941 ounce-inches, so the pound-inch 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-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 an Ounce-inch (ozf·in)?

An ounce-inch (ozf·in) is one ounce-force applied at one inch from the axis — the smallest of the common imperial torque units.

• 1 lbf·in = 16 ozf·in
• 1 lbf·ft = 192 ozf·in
• 1 ozf·in = 0.00706155 N·m

The Unit of Small Motors

Ounce-inches exist because small electric motors produce tiny torques that would be unreadable in pound-feet. A stepper motor rated at 0.35 lbf·ft is far more naturally described as 67 ozf·in, and that is how manufacturers publish it.

If you are choosing a stepper or servo for a 3D printer, CNC machine or robot, the datasheet holding-torque figure will almost certainly be in ozf·in or in N·cm.

Where Ounce-inch Is Used

• Stepper and servo motors — holding torque and detent torque ratings.
• Small gearmotors in appliances, printers and automation.
• Watchmaking and instrument work — miniature screws.
• Torque testing of caps, closures and small assemblies.

Converting Ounce-inch

Pound-inch to Ounce-inch Conversion Table

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