Joule (J)
The joule (J) is the SI unit of energy, work and heat: the work done by a force of one newton over one metre, or one watt for one second.
Symbol: J
Quantity: energy, work and heat
SI relation: J is the coherent SI unit of energy.
Derivation: 1 J = 1 N·m = 1 W·s = 1 kg·m²·s⁻²
Exact: yes, by definition
History
Named after James Prescott Joule, who measured the mechanical equivalent of heat in the 1840s.
Typical uses
- Physics and engineering energy balances
- Impact and ballistic energy
- Specific energy (J/kg) and heat capacity (J/(kg·K))
Convert joules to other units
| Conversion | 1 J equals | Reverse |
|---|---|---|
| joule to kilojoule | 0.001 kJ | kilojoule to joule |
| joule to kilocalorie | 0.0002390057361 kcal | kilocalorie to joule |
| joule to kilowatt-hour | 2.777777778 × 10⁻⁷ kWh | kilowatt-hour to joule |
| joule to BTU | 0.0009478171203 BTU | BTU to joule |
| joule to megajoule | 0.000001 MJ | megajoule to joule |
| joule to calorie | 0.2390057361 cal | calorie to joule |
| joule to watt-hour | 0.0002777777778 Wh | watt-hour to joule |
| joule to therm | 9.48043428 × 10⁻⁹ thm | therm to joule |
| joule to electronvolt | 6.241509074 × 10¹⁸ eV | electronvolt to joule |
| joule to foot-pound | 0.7375621493 ft·lbf | foot-pound to joule |
| joule to erg | 10000000 erg | erg to joule |
Open the Energy Converter to convert any value between all units.
Sources
- 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). Joule (J). Retrieved October 17, 2026, from https://scientificconverters.com/units/joule/
IEEE
Scientific Converters, "Joule (J)," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/units/joule/