⚡
Energy Converter
Convert energy between joules, calories, kWh, BTU and more.
Free · No sign-up · Updated August 2026
1 J = 0.001 kJ
| Unit | 1 J = |
|---|---|
| Joule | 1 J |
| Kilojoule | 0.001 kJ |
| Calorie | 0.23900574 cal |
| Kilocalorie | 0.00023901 kcal |
| Watt-hour | 0.00027778 Wh |
| Kilowatt-hour | 2.777778e-7 kWh |
| BTU | 0.00094782 BTU |
| Foot-pound | 0.73756215 ft·lb |
Converts instantly in your browser using precise factors. Nothing is uploaded.
🔒 This tool runs entirely in your browser. Your data is never uploaded.
Frequently asked questions
How many joules in a calorie?＋
1 (thermochemical) calorie = 4.184 joules. A food Calorie (kcal) = 4,184 joules.
Is it free and private?＋
Yes — it's free, needs no sign-up, and converts instantly in your browser.