Foot-Pounds Force (ft·lbf) to Joules (J) Converter
Enter a value to instantly convert between energy units.
1 Foot-Pound Force = 1.3558 Joule
Key Formulas
Kilocalorie → Kilojoule
kJ = kcal × 4.184Kilojoule → Kilocalorie
kcal = kJ × 0.239006Kilowatt-Hour → Joule
J = kWh × 3600000Joule → Kilowatt-Hour
kWh = J × 2.77778e-7Formula
J = ft·lbf × 1.3558179One foot-pound force equals exactly 1.3558179 joules, derived from 1 pound-force (4.4482 newtons) applied through 1 foot (0.3048 meters). Foot-pounds dominate US mechanical and automotive engineering, appearing in engine torque specs, machinery power ratings, and impact energy calculations. This conversion is essential for combining US equipment specifications with international SI-based engineering standards.
Source: NIST SP 811, Table B.8
Frequently Asked Questions
Real-World Examples
A US mechanical engineer documenting 1 ft·lbf torque requirement writes 1.356 J in SI documentation.
1 ft·lbf = 1.3558179 J
Car engine torque spec of 100 ft·lbf = 135.6 J (newton-meters) for metric torque wrench setting.
100 ft·lbf = 135.58179 J
1 horsepower defined as 550 ft·lbf per second = 745.7 joules per second = 745.7 watts.
550 ft·lbf = 745.7 J
Pneumatic impact wrench rated 250 ft·lbf = 339 J rotational energy for fastening specifications.
250 ft·lbf = 338.95 J