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

Pound-foot to Ounce-inch Conversion Formula

Example

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

Using the formula:

Therefore, 5 Pound-foot (lbf-ft) is equal to 960.00001135000001645 Ounce-inch (ozf-in).

How many pound-feet are in one ounce-inch? One Ounce-inch (ozf-in) contains 0.005208333271755643 Pound-feet (lbf-ft) — the inverse of the factor above. Multiplying by 192.00000227000000329 takes you from pound-feet to ounce-inches; multiplying by 0.005208333271755643 brings you back.

Put in words: one pound-foot equals 192.00000227000000329 ounce-inches, 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 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-foot to Ounce-inch Conversion Table

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