Foot Pound to Joule Converter
Convert foot pound joule between units instantly. Includes conversion tables, common equivalents, and calculation formulas.
Formula
J = ft-lbf x 1.35582 | 1 BTU = 1055.06 J | 1 cal = 4.184 J
One foot-pound equals 1.35582 joules. The joule is the SI unit of energy defined as the work done by a one-newton force through one meter. Key relationships: 1 BTU = 1,055.06 J, 1 calorie = 4.184 J, 1 kWh = 3,600,000 J. The foot-pound measures work in Imperial units (one pound of force through one foot).
Worked Examples
Example 1: Engine Torque Conversion
Problem: An engine produces 350 ft-lbf of torque. Convert to joules and newton-meters.
Solution: Joules: 350 x 1.35582 = 474.537 J\nNewton-meters: 474.537 Nm (same as joules for energy)\nKilojoules: 474.537 / 1000 = 0.4745 kJ\nBTU: 474.537 / 1055.06 = 0.4498 BTU
Result: 350 ft-lbf = 474.54 J = 474.54 Nm
Example 2: Energy Comparison
Problem: Convert 5,000 joules to foot-pounds, calories, and BTU.
Solution: Foot-pounds: 5,000 / 1.35582 = 3,688.10 ft-lbf\nCalories: 5,000 / 4.184 = 1,195.22 cal\nKilocalories: 5,000 / 4,184 = 1.195 kcal\nBTU: 5,000 / 1,055.06 = 4.739 BTU
Result: 5,000 J = 3,688.1 ft-lbf = 1,195.2 cal = 4.74 BTU
Frequently Asked Questions
How do I convert foot-pounds to joules?
To convert foot-pounds to joules, multiply by 1.35582. One foot-pound (ft-lbf) is the energy needed to exert a force of one pound through a distance of one foot. For example, 100 foot-pounds equals 135.582 joules. The foot-pound is commonly used in US engineering for torque specifications on engines and fasteners, while the joule is the SI standard energy unit used internationally.
What is the difference between a foot-pound of energy and a foot-pound of torque?
A foot-pound of energy (ft-lbf) and a foot-pound of torque (lb-ft) have the same dimensions but different physical meanings. Energy foot-pounds measure work done when a force moves through a distance. Torque foot-pounds (often written lb-ft in automotive contexts) measure rotational force around an axis. Numerically they are equivalent, but conventionally energy uses ft-lbf while torque uses lb-ft to distinguish the concepts.
What is an erg and how does it relate to a joule?
An erg is the CGS (centimeter-gram-second) unit of energy equal to exactly 0.0000001 joules (10^-7 J). One joule equals 10 million ergs. The erg is defined as the work done by a force of one dyne acting through one centimeter. While largely replaced by the joule in modern science, ergs still appear in astrophysics literature where extremely large energies are expressed in ergs. A supernova releases about 10^44 joules or 10^51 ergs of energy.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
Can I use the results for professional or academic purposes?
You may use the results for reference and educational purposes. For professional reports, academic papers, or critical decisions, we recommend verifying outputs against peer-reviewed sources or consulting a qualified expert in the relevant field.
Does Foot Pound to Joule Converter work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.