Convert Foot-pounds to Joules
1 foot-pound (ft·lbf) equals 1.355817948 joules (J).
1 ft·lbf = 1.355817948 J
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk foot-pound to joule converter to paste a column from Excel.
How to Convert Foot-pound to Joule
- 1 ft·lbf = 1.355817948 J
- 1 J = 0.7375621493 ft·lbf
- Example: convert 15 ft·lbf to J: 15 ft·lbf = 15 × 1.355817948 J = 20.33726922 J
Formula
J = ft·lbf × 1.355817948331
Derivation from SI units:
- 1 ft·lbf = 0.3048 m × 4.4482216152605 N = 1.3558179483314 J
- 1 J = 1 N·m = 1 W·s = 1 kg·m²·s⁻²
Both units are defined exactly, so the factor is exact. Foot-pound definition: foot-pound; Joule definition: joule.
Worked examples
- An air rifle with 12 ft·lbf of muzzle energy delivers 16.26981538 J.
12 ft·lbf × 1.355817948 = 16.26981538 J - 1000 ft·lbf is 1355.817948 J.
1000 ft·lbf × 1.355817948 = 1355.817948 J
Foot-pound to Joule conversion table
| Foot-pounds (ft·lbf) | Joules (J) |
|---|---|
| 1 ft·lbf | 1.355817948 J |
| 5 ft·lbf | 6.779089742 J |
| 10 ft·lbf | 13.55817948 J |
| 25 ft·lbf | 33.89544871 J |
| 50 ft·lbf | 67.79089742 J |
| 100 ft·lbf | 135.5817948 J |
| 250 ft·lbf | 338.9544871 J |
| 500 ft·lbf | 677.9089742 J |
| 1000 ft·lbf | 1355.817948 J |
| 2000 ft·lbf | 2711.635897 J |
Where it's used
Muzzle energy, impact energy and work in foot-pounds are converted to joules for SI and international rules.
Foot-pound to other energy units
| Conversion | 1 ft·lbf equals |
|---|---|
| foot-pound to joule | 1.355817948 J |
| foot-pound to kilojoule | 0.001355817948 kJ |
| foot-pound to megajoule | 0.000001355817948 MJ |
| foot-pound to calorie | 0.3240482668 cal |
| foot-pound to kilocalorie | 0.0003240482668 kcal |
| foot-pound to watt-hour | 0.0003766160968 Wh |
| foot-pound to kilowatt-hour | 3.766160968 × 10⁻⁷ kWh |
| foot-pound to BTU | 0.001285067463 BTU |
| foot-pound to therm | 1.285374295 × 10⁻⁸ thm |
| foot-pound to electronvolt | 8.462350028 × 10¹⁸ eV |
| foot-pound to erg | 13558179.48 erg |
Frequently asked questions
How many joules is 1 ft·lb?
1 ft·lbf = 1.355817948331 J.
How many joules are in 1 foot-pound?
1 ft·lbf = 1.355817948 J.
How do I convert foot-pounds to joules?
Multiply the value in ft·lbf by 1.355817948. For example, 15 ft·lbf × 1.355817948 = 20.33726922 J.
Is the ft·lbf to J conversion exact?
Yes. Both units are defined exactly, so the ratio is exact; its decimal form does not terminate and is shown here to 10 significant figures (more with the precision selector).
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "foot pound-force (ft·lbf)".
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4, coherent derived units with special names.
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Foot-pounds to Joules. Retrieved October 17, 2026, from https://scientificconverters.com/energy/foot-pounds-to-joules/
IEEE
Scientific Converters, "Convert Foot-pounds to Joules," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/energy/foot-pounds-to-joules/