Foot-Pound to Inch-Pound Formula and Calculator

Convert foot-pounds to inch-pounds by multiplying the foot-pound value by 12: inch-pounds = foot-pounds × 12. Enter a value in foot-pounds below to get the equivalent torque or energy value in inch-pounds.

Formula

The conversion formula is:

in·lb = ft·lb × 12

• ft·lb is the value in foot-pounds.
• in·lb is the equivalent value in inch-pounds.
• 12 is the number of inches in one foot.

The conversion works because a foot-pound and an inch-pound use the same pound-force unit but different distance units. One foot is 12 inches, so a pound of force acting through one foot corresponds to the same amount of work or torque as that force acting through 12 inches. The calculator also gives joules as a metric energy equivalent: 1 foot-pound-force is approximately 1.35581795 joules. The joule result is rounded to two decimal places.

Worked Example

Using the calculator’s default input of 1 ft·lb:

1. Start with 1 foot-pound.
2. Multiply by 12 inches per foot: 1 × 12 = 12.
3. The result is 12 in·lb.
4. For the additional metric result, calculate 1 × 1.3558179483314 = 1.3558179483314 J, which rounds to 1.36 J.

What Foot-Pounds and Inch-Pounds Measure

A foot-pound can describe work or energy: one pound-force doing work over a distance of one foot. An inch-pound uses the same idea over one inch. These are customary units; the corresponding SI energy unit is the joule. Because torque is also force multiplied by a distance, foot-pounds and inch-pounds are commonly used for torque specifications too.

Although the arithmetic conversion is the same, the physical quantity and context matter. Work or energy is often written as ft·lbf or in·lbf, while torque is often written as lbf·ft or lbf·in. The notation can vary, so check the surrounding document or instrument to see whether it is discussing torque or energy. The conversion changes the distance unit, not the type of quantity being measured.

For torque, the direction of the force relative to the lever arm also matters. The simple unit conversion does not calculate torque from a force and geometry; it only converts a torque value already expressed in one of these units.

How to Use the Conversion

• Identify the number and confirm that it is expressed in foot-pounds, not inch-pounds or another unit.
• Multiply the number by 12 to convert to inch-pounds.
• Keep the unit attached to the result. For example, 2.5 ft·lb × 12 = 30 in·lb.
• If you need joules, multiply the foot-pound value by approximately 1.35581795. For 2.5 ft·lb, that is about 3.39 J.

To convert in the opposite direction, divide inch-pounds by 12. For instance, 30 in·lb ÷ 12 = 2.5 ft·lb. Multiplying by 12 converts from the larger distance unit to the smaller one, so the numerical value increases; dividing reverses the conversion.

Common Conversion Mistakes

• Multiplying in the wrong direction: ft·lb to in·lb means multiply by 12. in·lb to ft·lb means divide by 12.
• Confusing torque with energy: Both can involve force times distance and may share unit names, but they describe different things. A conversion does not make a torque value into energy or vice versa.
• Mixing pound-force and pound-mass: In these customary force-distance units, “pound” refers to pound-force. Pound-mass is a different quantity and cannot be substituted without the relevant physical context.
• Rounding too early: The factor 12 is exact, so preserve the input’s useful precision through the multiplication and round only the final display as appropriate.
• Reading a decimal as a whole number: 0.5 ft·lb is 6 in·lb, not 0.5 in·lb. The unit change affects the number even though the physical quantity is unchanged.

Accuracy, Notation, and Limits

The foot-to-inch factor is exact: 1 ft = 12 in. Therefore, multiplying by 12 does not introduce conversion-factor approximation. The calculator displays the inch-pound answer as a whole number because the conversion itself produces an exact multiple of the entered value; if an input has a fractional part, the displayed whole-number output may conceal that precision. For a precise fractional result, calculate with the formula and retain the needed decimal places.

The joule factor shown is a rounded representation of the relationship between customary foot-pound-force and SI energy units, so its output is appropriately rounded. This calculator accepts nonnegative values; if a technical convention uses a signed torque to indicate direction, keep that sign separately or use a signed calculation appropriate to the application. The conversion alone does not validate a measurement, a device setting, or a specification.

For metric torque, the related units are newton-metres (N·m) and newton-centimetres (N·cm). One N·m equals 100 N·cm. A joule has the same dimensions as a newton-metre for work, but torque is conventionally written N·m to distinguish it from energy in context. Do not infer that two quantities are interchangeable just because their units have the same dimensions.

Frequently Asked Questions

How many inch-pounds are in one foot-pound?
There are 12 inch-pounds in one foot-pound: 1 ft·lb = 12 in·lb.

How do I convert inch-pounds to foot-pounds?
Divide the inch-pound value by 12. For example, 48 in·lb ÷ 12 = 4 ft·lb.

Is ft-lb the same as lb-ft?
Both notations are commonly used for pound-force times feet, especially for torque, but notation conventions vary. Read the surrounding context and identify whether the value represents torque or work.

How many joules are in a foot-pound?
One foot-pound-force is approximately 1.35581795 joules. For example, 10 ft·lb is approximately 13.56 J.

Does converting foot-pounds to inch-pounds change the torque?
No. It changes only the unit expression. The physical torque remains the same when the value is multiplied by 12 and expressed in inch-pounds instead of foot-pounds.

Related

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• Power from Torque and RPM: Formula and Calculator
• Work in Physics: Formula, Units, and Examples

in ft_lb | Foot-pounds | ft·lb | 1 | 0
out in_lb | Inch-pounds | in·lb | ft_lb * 12 | 0
out joules | Joules | J | ft_lb * 1.3558179483314 | 2