How to Convert Inch-Pounds to Foot-Pounds
Converting inch-pounds to foot-pounds is a simple unit conversion used frequently in mechanics, engineering, automotive repair, construction, and tool specifications. To give you an idea, 24 inch-pounds equals 2 foot-pounds. And because 1 foot equals 12 inches, you divide the number of inch-pounds by 12 to obtain foot-pounds. The key is understanding whether the measurement represents torque or mechanical work, as both types can be expressed in inch-pounds and foot-pounds.
Understanding Inch-Pounds and Foot-Pounds
An inch-pound, commonly abbreviated as in-lb, in-lbs, or lb-in, is a measurement of force applied over a distance of one inch. A foot-pound, abbreviated as ft-lb, ft-lbs, or lb-ft, uses a distance of one foot Turns out it matters..
When the measurement describes torque, it indicates the turning effect of a force. Torque depends on two factors:
- The amount of force being applied
- The length of the lever arm over which the force acts
Torque is commonly written as:
Torque = Force × Lever-Arm Distance
The same general relationship also applies to mechanical work:
Work = Force × Distance
For this reason, inch-pounds and foot-pounds are often used interchangeably in everyday mechanical discussions. Even so, context matters. A specification such as “tighten this bolt to 75 ft-lb” usually refers to torque, while a statement such as “moving this load required 75 ft-lb of work” refers to energy.
The Basic Conversion Formula
To convert inch-pounds to foot-pounds, divide by 12:
Foot-pounds = Inch-pounds ÷ 12
You can also write this as:
ft-lb = in-lb ÷ 12
The reverse conversion works in the opposite direction:
Inch-pounds = Foot-pounds × 12
Quick Conversion Examples
| Inch-Pounds | Foot-Pounds |
|---|---|
| 12 in-lb | 1 ft-lb |
| 24 in-lb | 2 ft-lb |
| 36 in-lb | 3 ft-lb |
| 60 in-lb | 5 ft-lb |
| 120 in-lb | 10 ft-lb |
| 240 in-lb | 20 ft-lb |
| 600 in-lb | 50 ft-lb |
Recognizing these common values can make mental calculations much faster But it adds up..
Example: Converting 48 Inch-Pounds to Foot-Pounds
Suppose a mechanic has a torque specification written as 48 inch-pounds and needs the equivalent value in foot-pounds.
Using the formula:
ft-lb = 48 ÷ 12
ft-lb = 4
Therefore:
48 inch-pounds = 4 foot-pounds
This is especially useful when a manual specifies inch-pounds but the torque wrench is calibrated in foot-pounds.
More Worked Examples
Example 1: Converting 30 Inch-Pounds
30 ÷ 12 = 2.5
So, 30 inch-pounds equals 2.5 foot-pounds.
Example 2: Converting 75 Inch-Pounds
75 ÷ 12 = 6.25
So, 75 inch-pounds equals 6.25 foot-pounds Worth keeping that in mind..
Example 3: Converting 250 Inch-Pounds
250 ÷ 12 = 20.8333…
Rounded to two decimal places:
250 inch-pounds equals approximately 20.83 foot-pounds Worth knowing..
Example 4: Converting a Fractional Measurement
Suppose the torque is 7.5 inch-pounds:
7.5 ÷ 12 = 0.625
Therefore:
7.5 inch-pounds = 0.625 foot-pounds
For very small measurements, converting to a fraction may be more useful than expressing the result as a decimal:
7.5 in-lb = 7.5/12 ft-lb = 5/8 ft-lb
Example 5: Converting Foot-Pounds Back to Inch-Pounds
If a specification is 9 foot-pounds, multiply by 12:
9 × 12 = 108
Therefore:
9 foot-pounds = 108 inch-pounds Not complicated — just consistent..
Converting Torque on a Torque Wrench
Torque values are frequently written in foot-pounds on repair manuals, even when the tool being used displays inch-pounds. This is particularly common with smaller fasteners and delicate components.
If your torque wrench is marked in inch-pounds:
- Find the required torque in foot-pounds.
- Divide that number by 12.
- Set the wrench to the resulting inch-pound value.
To give you an idea, a manual might specify 18 ft-lb, while the wrench is calibrated in inch-pounds:
18 × 12 = 216 in-lb
Set the wrench to **216 inch
