Work from one pound-force over one foot.
Foot-pounds to Joules Converter — ft-lb to J
Convert Foot-pound (ft-lb) to Joule (J) using the exact conversion factor (1 foot-pound = 1.355817948 joule). See the formula, worked examples, conversion table, history, and common uses.
Foot-pounds to Joules converter
Converter
Engineering Converter
Convert common stress, force, torque, power, and energy units used in engineering.
Context values
Some unit families need one extra value for a physically accurate result.
The joule is the SI derived unit of energy.
Result = input x 1.355817948 / 1.
Energy units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Foot-pounds to Joules
Foot-pound and Joule both measure a quantity used in structural or mechanical engineering — commonly stress, pressure, force, torque, power, or energy — where converting between the unit conventions used in different regions, industries, or equipment specifications is a routine part of design work. Specifically: Work from one pound-force over one foot, and the joule is the SI derived unit of energy.
Formula
joules = foot-pounds × 1.35581794833
This factor comes from each unit's defined relationship to the category's base unit: 1 foot-pound equals 1.35581794833 base units, and 1 joule equals 1 base unit, so dividing one by the other gives the direct foot-pound-to-joule factor of 1.35581794833.
Simple example
1 ft-lb × 1.355817948 = 1.355817948 J
1 foot-pound = 1.355817948 joules.
Real-world example
100 ft-lb × 1.355817948 = 135.5817948 J
100 foot-pounds = 135.5817948 joules.
Conversion table
| Foot-pound (ft-lb) | Joule (J) |
|---|---|
| 1 ft-lb | 1.355817948 J |
| 10 ft-lb | 13.55817948 J |
| 50 ft-lb | 67.79089742 J |
| 100 ft-lb | 135.5817948 J |
| 500 ft-lb | 677.9089742 J |
| 1,000 ft-lb | 1,355.817948 J |
Reverse conversion: Joule to Foot-pound
1.355817948 J × 0.7375621493 = 0.9999999998 ft-lb
1.355817948 joules = 0.9999999998 foot-pounds.
foot-pounds = joules × 0.737562149277
For a page dedicated to this direction, see Joule to Foot-pound.
Understanding the Foot-pound (ft-lb)
Work from one pound-force over one foot.
Understanding the Joule
Joule (J) measures energy. The joule is the SI derived unit of energy, defined as the work done by one newton acting over one meter. It is classified as a SI derived unit.
Where it's used: Standard scientific and engineering energy unit worldwide
Uses of the Joule today
- Physics and engineering energy calculations
- Electrical energy in scientific contexts (though kWh is used for billing)
- Nutrition labeling in some countries (alongside or instead of calories)
History of the Joule
The joule is named after English physicist James Prescott Joule, whose experiments in the 1840s established the mechanical equivalent of heat — demonstrating that mechanical work and heat are interchangeable forms of energy, foundational to the first law of thermodynamics.
The unit itself was formally adopted as the SI derived unit of energy by international agreement as part of the broader SI system, defined coherently from the base units (kg, m, s) rather than as an independent physical standard.
Historical origin. Joule was not the invention of a single named person; it developed through the process described above.
Joule — sources
- BIPM SI Brochure — Coherent derived units — Defines the joule as the SI unit of energy.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many joules are in 1 foot-pound?
1 foot-pound equals 1.355817948 joules, using the exact defined conversion factor rather than an estimate.
How do I convert foot-pound to joule?
Multiply the foot-pound value by 1.355817948. The converter above does this instantly to whatever precision you set.
How do I convert joule back to foot-pound?
Use the reverse factor: 1 joule equals 0.7375621493 foot-pounds. You can also use the swap control in the converter above to flip the direction instantly.
What is a foot-pound?
Foot-pound (ft-lb) is a unit of engineering.
What is a joule?
Joule (J) measures energy. The joule is the SI derived unit of energy, defined as the work done by one newton acting over one meter. It is classified as a SI derived unit.
Is the foot-pound to joule conversion exact?
Yes. Both foot-pound and joule are defined by fixed standards rather than physical artifacts, so the factor of 1.355817948 used above is exact to as many digits as you choose to display.
Why do engineering unit conventions vary so much by region and industry?
Pressure, force, and stress can be expressed in metric (pascal, newton), US customary (psi, pound-force), or older and industry-specific units (atmosphere, torr, kip) depending on the country, industry, and even the equipment manufacturer, which is why engineers routinely need to convert between them when working across specs from different sources.