Energy Converter — Joules, Calories, kWh, BTU, eV
Convert energy between Joules, calories, kilocalories, kWh, BTU, and electronvolts instantly.
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Formula
All Units
Energy Unit Reference
| Unit | Symbol | In Joules |
|---|---|---|
| Joule | J | 1 |
| Kilojoule | kJ | 1,000 |
| Calorie | cal | 4.184 |
| Kilocalorie | kcal | 4,184 |
| Kilowatt-hour | kWh | 3,600,000 |
| BTU | BTU | 1,055.06 |
| Electronvolt | eV | 1.602 × 10⁻¹⁹ |
Frequently Asked Questions
How many Joules are in a calorie?
1 calorie (small calorie, cal) = 4.184 Joules. 1 kilocalorie (kcal or Calorie with capital C) = 4,184 Joules. Food energy is measured in kcal.
What is a kilowatt-hour (kWh)?
1 kWh = 3,600,000 Joules (3.6 MJ). It is the energy unit used on electricity bills. Using a 1,000W appliance for 1 hour consumes 1 kWh.
What is a BTU?
BTU (British Thermal Unit) is the energy required to raise 1 pound of water by 1°F. 1 BTU = 1,055.06 Joules. Used for air conditioner and heater ratings.
What is an electronvolt (eV)?
1 eV = 1.602 × 10⁻¹⁹ Joules. It is an extremely small unit used in atomic and particle physics to describe the energy of subatomic particles.
How do I convert kcal to kJ?
1 kcal = 4.184 kJ. So multiply kcal by 4.184 to get kilojoules. This conversion is common in nutrition labelling in many countries.