Foot-pound to Joule Converter
Enter the value that you want to convert foot-pound (ft*lbf) to joule (J) or joule to foot-pound.
1 foot-pound = 1.3558179 joule
Formula: joule = foot-pound value × 1.3558179
FT*LBF to J — foot-pound to joule
10 foot-pound = 13.55818 joule
Popular Energy Converters:
Foot-pound vs Joule
What is Foot-pound?
Foot-pound (ft*lbf) is a unit of energy measurement. 1 foot-pound is equal to 1.3558179 joule.
The Joule in Engineering
Joule (J) is a unit of energy measurement. 1 joule is equal to 0.7375621 foot-pound.
Energy Units in Different Fields
Energy measurement units reflect their historical origins across different industries. Electrical engineers use kilowatt-hours, nutritionists use calories, physicists use joules, heating engineers use BTUs, and the petroleum industry uses barrels of oil equivalent. Converting between these units is essential for energy auditing, comparing fuel sources, sizing HVAC systems, and understanding electricity bills relative to gas consumption.
foot-pound to joule metric conversion table
| 0.01 ft*lbf | = | 0.01356 J |
| 0.1 ft*lbf | = | 0.13558 J |
| 1 ft*lbf | = | 1.35582 J |
| 2 ft*lbf | = | 2.71164 J |
| 3 ft*lbf | = | 4.06745 J |
| 4 ft*lbf | = | 5.42327 J |
| 5 ft*lbf | = | 6.77909 J |
| 6 ft*lbf | = | 8.13491 J |
| 7 ft*lbf | = | 9.49073 J |
| 8 ft*lbf | = | 10.84654 J |
| 9 ft*lbf | = | 12.20236 J |
| 10 ft*lbf | = | 13.55818 J |
| 11 ft*lbf | = | 14.91400 J |
| 12 ft*lbf | = | 16.26982 J |
| 13 ft*lbf | = | 17.62563 J |
| 14 ft*lbf | = | 18.98145 J |
| 15 ft*lbf | = | 20.33727 J |
| 16 ft*lbf | = | 21.69309 J |
| 17 ft*lbf | = | 23.04891 J |
| 18 ft*lbf | = | 24.40472 J |
| 19 ft*lbf | = | 25.76054 J |
| 20 ft*lbf | = | 27.11636 J |
| 30 ft*lbf | = | 40.67454 J |
| 40 ft*lbf | = | 54.23272 J |
| 50 ft*lbf | = | 67.79090 J |
| 60 ft*lbf | = | 81.34908 J |
| 70 ft*lbf | = | 94.90726 J |
| 80 ft*lbf | = | 108.46544 J |
| 90 ft*lbf | = | 122.02362 J |
| 100 ft*lbf | = | 135.58179 J |
| 200 ft*lbf | = | 271.16359 J |
| 300 ft*lbf | = | 406.74538 J |
| 400 ft*lbf | = | 542.32718 J |
| 500 ft*lbf | = | 677.90897 J |
| 600 ft*lbf | = | 813.49077 J |
| 700 ft*lbf | = | 949.07256 J |
| 800 ft*lbf | = | 1084.65436 J |
| 900 ft*lbf | = | 1220.23615 J |
| 1000 ft*lbf | = | 1355.81795 J |
How to Convert FT*LBF to J (Foot-pound to Joule)?
We can convert foot-pound to joule by using an example.
Example:
Convert 20 Foot-pound to Joule?
We know 1 Foot-pound = 1.3558179 joule; 1 Joule = 0.7375621 foot-pound.
20 foot-pound = ___J
20 × 1.3558179 = 27.11636 J (we know 1 foot-pound = 1.3558179 joule)
Answer:
20 foot-pound = 27.11636 joule
How to Convert Foot-Pounds to Joules (Step-by-Step)
The foot-pound (ft·lb or ft-lbf) is a US customary unit of energy or work, while the joule is the SI standard. The conversion factor is 1 ft-lb = 1.35582 J. This conversion is essential in mechanical engineering, physics labs, and torque specifications.
- Identify the energy or work value in foot-pounds.
- Multiply by 1.35582 to convert to joules.
- Note: ft-lb (energy) and lb-ft (torque) have the same magnitude but different applications.
- Round to appropriate significant figures.
Common Foot-Pounds to Joules Conversions
Reference values for mechanical work and energy measurements, converting US customary ft-lb to SI joules.
| Foot-pound | Joule |
|---|---|
| 1 ft-lb | 1.356 J |
| 10 ft-lb | 13.56 J |
| 25 ft-lb | 33.9 J |
| 100 ft-lb | 135.6 J |
| 250 ft-lb | 338.9 J |
| 500 ft-lb | 677.9 J |
| 778 ft-lb | 1,055 J (≈1 BTU) |
Solved Examples: Foot-Pounds to Joules
Question 1: A physics experiment measures 45 ft-lb of work done. Express in joules.
Solution:
Start with 45 ft-lb.
Multiply by 1.35582: 45 × 1.35582 = 61.01 J.
Answer: 45 ft-lb = 61.01 J
Question 2: A bullet has muzzle energy of 1,200 ft-lb. Convert to joules.
Solution:
Start with 1,200 ft-lb.
Multiply by 1.35582: 1,200 × 1.35582 = 1,627.0 J.
Express in kJ: 1,627.0 ÷ 1000 = 1.627 kJ.
Answer: 1,200 ft-lb = 1,627 J ≈ 1.63 kJ
Question 3: You push a 50-lb object 20 feet along the ground (against 10 lb of friction). Work done?
Solution:
Work = Force × Distance = 10 lb × 20 ft = 200 ft-lb.
Convert to joules: 200 × 1.35582 = 271.2 J.
Answer: 200 ft-lb of work = 271.2 J
Practice: Foot-Pounds to Joules
Try solving these on your own to test your understanding:
- Convert 75 ft-lb to joules. (Answer: 101.7 J)
- A spring stores 30 ft-lb of energy. Express in joules. (Answer: 40.67 J)
- Convert 500 ft-lb to joules. (Answer: 677.9 J)
- A pendulum has 8 ft-lb of kinetic energy. Convert to joules. (Answer: 10.85 J)
- Convert 1,500 ft-lb to kJ. (Answer: 2.034 kJ)
Foot-Pounds in Physics Labs
In US physics courses, students frequently encounter ft-lb in mechanical work problems: lifting objects, spring compression, and friction calculations. The formula W = F × d gives work in ft-lb when force is in pounds-force and distance in feet. To convert these results to SI (joules) for comparison with textbook values, multiply by 1.35582. Many physics labs require students to perform calculations in both systems to develop unit conversion fluency.
The Mechanical Equivalent of Heat
Historically, James Joule demonstrated that 778 ft-lb of mechanical work produces 1 BTU of heat (Joule's famous paddle wheel experiment, 1843). In modern SI units: 778 × 1.35582 = 1,055 J ≈ 1 BTU. This experiment established that heat and mechanical work are both forms of energy, leading to the law of conservation of energy and the naming of the joule unit in Joule's honor.
Torque vs Energy: Same Unit, Different Meaning
Foot-pound (ft-lb) as energy means the work done by 1 pound-force over 1 foot of distance. Pound-foot (lb-ft) as torque means 1 pound-force applied at 1 foot radius. They are dimensionally equivalent (force × length) but conceptually different. Energy is a scalar (total work done), while torque is a vector (rotational tendency). When converting torque specifications, use the same 1.35582 factor to get newton-meters (N·m).
Key Takeaways
- Multiply ft-lb by 1.35582 to get joules.
- 778 ft-lb = 1 BTU = 1,055 J (the mechanical equivalent of heat).
- ft-lb (energy) and lb-ft (torque) have the same numerical conversion factor to SI.
- Quick estimate: ft-lb × 1.4 gives joules within 3% accuracy.
- Named after James Joule, who quantified the relationship between work and heat.
- Common in US physics, ballistics, and mechanical engineering contexts.
Foot-pound to Joule Conversion Formula
joule = foot-pound × 1.3558179
1 foot-pound = 1.3558179 joule
1 joule = 0.7375621 foot-pound
Reverse: foot-pound = joule × 0.7375621
Frequently Asked Questions
How many joule are in 1 foot-pound?
There are 1.3558179 joule in 1 foot-pound. To convert foot-pound to joule, multiply the value by 1.3558179.
How do I convert foot-pound to joule?
Multiply your foot-pound value by 1.3558179 to get the equivalent in joule. For example, 5 foot-pound = 5 × 1.3558179 = 6.77909 joule.
How do I convert joule to foot-pound?
Multiply your joule value by 0.7375621 to get the equivalent in foot-pound. Alternatively, divide by 1.3558179.
What is 10 foot-pound in joule?
10 foot-pound is equal to 13.55818 joule.
What is 100 foot-pound in joule?
100 foot-pound is equal to 135.58179 joule.