Relationship Between Foot-Pounds and Inch-Pounds

The conversion between foot-pounds and inch-pounds is based on the relationship between feet and inches in distance. Since 1 foot equals 12 inches, one foot-pound of torque equals 12 inch-pounds of torque.

1 ft·lb = 12 in·lb

Therefore, to convert foot-pounds to inch-pounds, we multiply the value in foot-pounds by 12.

For example, 1 foot-pound equals 12 inch-pounds, and 10 foot-pounds equals 120 inch-pounds.

Foot-Pound

What is a Foot-Pound (ft·lb)?

A foot-pound (symbol: ft·lb) is a unit of torque in the imperial system, representing the rotational force of one pound applied at a perpendicular distance of one foot from the axis of rotation. It equals approximately 1.35582 Newton meters. Foot-pounds are widely used in the United States for automotive, mechanical, and engineering applications.

Origin

The foot-pound has been used for centuries as a measure of work and torque in English-speaking countries. It derives from the imperial system's basic units of force (pound-force) and distance (foot). While the term 'foot-pound' can refer to both work (energy) and torque, context usually makes the meaning clear. In torque applications, it's sometimes written as 'pound-foot' (lbf·ft) to distinguish it from the energy unit, though foot-pound (ft·lb) remains more common in everyday use.

Current Use

Foot-pounds are the standard unit for torque specifications in the United States and some other countries using imperial measurements. Common applications include: automotive lug nuts (80-100 ft·lb), engine cylinder head bolts (50-90 ft·lb), bicycle pedals (30-35 ft·lb), oil drain plugs (15-25 ft·lb), and various machinery fasteners. Torque wrenches are typically calibrated in foot-pounds for these applications. While most countries have adopted the metric Newton meter, foot-pounds remain dominant in American automotive and mechanical industries.

Inch-Pound

What is an Inch-Pound (in·lb)?

An inch-pound (symbol: in·lb) is a unit of torque in the imperial system, representing the rotational force of one pound applied at a perpendicular distance of one inch from the axis of rotation. It is commonly used for smaller torque specifications where foot-pounds would be too large, such as in electronics assembly, precision equipment, and small fasteners.

History and Origin of the Inch-Pound

The inch-pound evolved from the imperial system of measurement as a natural subdivision of the foot-pound. As manufacturing and engineering became more precise, there was a need for smaller torque units to specify tightening specifications for smaller fasteners and delicate components. The inch-pound became standard in industries requiring precision torque measurements, particularly in aerospace, electronics, and automotive applications.

Modern Applications of Inch-Pounds

Inch-pounds are extensively used in various industries for precision torque applications. Common uses include: electronics assembly (2-10 in·lb), computer hard drive screws (3-6 in·lb), smartphone and tablet assembly (2-5 in·lb), bicycle component screws (5-25 in·lb), small engine fasteners (10-50 in·lb), and precision instruments. Torque wrenches and screwdrivers calibrated in inch-pounds are essential tools in these fields. The unit is particularly prevalent in the United States, while metric countries typically use Newton centimeters (N·cm) or millinewton meters (mN·m) for similar applications.

Foot-Pound to Inch-Pound Conversion Table

The conversion of foot-pounds to inch-pounds for certain values are provided below: