Foot-Pounds to Joules Converter

How it is calculated

The conversion is a single multiplication or division by a fixed factor: 1 ft·lb = 1.3558179483 J. Foot-pounds to joules: J = ft·lb × 1.3558179483. Joules to foot-pounds: ft·lb = J ÷ 1.3558179483, which is the same as multiplying by about 0.737562. The factor comes from the foot (0.3048 m) and the pound-force (using standard gravity of 9.80665 m/s²). Results are shown with six decimals. The tool also prints the factor for the chosen direction and echoes your input in the original unit. Zero and negative values are accepted. Because one foot-pound of work and one pound-foot of torque have the same size, a torque in lb·ft converts to newton-metres with the same factor, even though the tool labels the result in joules.

Common mistakes

• Choosing the wrong direction. Converting 150 as joules when it is in foot-pounds gives 110.6 instead of 203.4, and the tool will not warn you.
• Dividing when you should multiply. Going from ft·lb to J makes the number larger, going from J to ft·lb makes it smaller.
• Confusing foot-pounds with pound-feet in context. They have the same numerical conversion, but energy and torque are different quantities and should not be mixed in a calculation.
• Reading the reverse line as a second conversion. It only repeats the number you typed in its original unit, so it will always match your input.
• Using the rounded 1.356 and carrying that through a long calculation. The tool uses the full factor with ten digits.