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Energy Converter
Convert energy units for electricity, nutrition, heating, physics, batteries, and engineering work.
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Instant results1 joule [J] = 0.001 kilojoule [kJ]
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| Unit | Symbol | Conversion factor | Quick links |
|---|---|---|---|
| joule | J | Base unit | Reference unit |
| kilojoule | kJ | 1 kilojoule [kJ] = 1000 J | to J from J |
| calorie | cal | 1 calorie [cal] = 4.184 J | to J from J |
| kilocalorie | kcal | 1 kilocalorie [kcal] = 4184 J | to J from J |
| watt-hour | Wh | 1 watt-hour [Wh] = 3600 J | to J from J |
| kilowatt-hour | kWh | 1 kilowatt-hour [kWh] = 3600000 J | to J from J |
| electronvolt | eV | 1 electronvolt [eV] = 1.602177E-19 J | to J from J |
| British thermal unit | BTU | 1 British thermal unit [BTU] = 1055.055853 J | to J from J |
| foot-pound | ft-lb | 1 foot-pound [ft-lb] = 1.355818 J | to J from J |
| therm (US) | therm | 1 therm (US) [therm] = 105480400 J | to J from J |
Accuracy and Sources
Energy factors use joule as the reference unit, including electrical, thermal, food-energy, and mechanical work units. Content was last reviewed on 2026-05-21. For safety-critical work, confirm results against the relevant official standard.
How energy conversion works
Energy conversion changes a measurement from one unit to another using a fixed factor or formula. Use the calculator above for instant results, then check the table and related converter links for common values.
Frequently Asked Questions
View sitemap →What is the base unit for energy?
The reference base unit used on this page is J.
Are these energy conversions accurate?
Yes, the calculator uses the conversion factors listed on the page. For critical work, verify results with an authoritative standard.