Energy Converter
Convert between energy units — joules (J), calories (cal), kilocalories (kcal), kilowatt-hours (kWh), and British Thermal Units (BTU). Used in physics, nutrition, engineering and electricity calculations.
Energy Units Reference Table
Common energy unit equivalents. 1 kcal (food Calorie) = 4,184 J. 1 kWh = 3,600,000 J.
| Unit | cal | kcal | kWh | BTU |
|---|---|---|---|---|
| 1 Joule (J) | 0.2388 | 0.000239 | 2.778e-7 | 0.000948 |
| 1 Calorie (cal) | 1 | 0.001 | 1.163e-6 | 0.003966 |
| 1 Kilocalorie (kcal) | 1,000 | 1 | 0.001163 | 3.966 |
| 1 Kilowatt-hour (kWh) | 860,421 | 860.4 | 1 | 3,412 |
| 1 BTU | 252.2 | 0.2522 | 0.000293 | 1 |
| 1 Watt-hour (Wh) | 860.4 | 0.8604 | 0.001 | 3.412 |
| 1 Electronvolt (eV) | 3.827e-20 | 3.827e-23 | 2.778e-26 | 1.519e-22 |
Real-World Energy Reference
| Context | Energy |
|---|---|
| Resting calorie burn (1 hr) | ~70 kcal (293 kJ) |
| Average banana | ~90 kcal (376 kJ) |
| 1 hour of cycling | ~400–600 kcal |
| LED bulb (10W, 1 hr) | 0.01 kWh (36 kJ) |
| Typical home (daily) | ~10–30 kWh |
| Car fuel tank (50L petrol) | ~430 kWh (1,550 MJ) |
| Lightning bolt | ~1–5 GJ (278–1,389 kWh) |
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About Energy Units
Energy is the capacity to do work. The SI unit is the joule (J). In everyday life, food energy is measured in kilocalories (kcal) — the "calories" on nutrition labels. 1 food Calorie (capital C) = 1 kcal = 4,184 J.
Electricity is billed in kilowatt-hours (kWh). 1 kWh = 3,600,000 J = 860.4 kcal. British Thermal Units (BTU) are used in heating and air conditioning in the US — 1 BTU is the energy needed to raise 1 pound of water by 1°F.
Important distinction: a calorie (lowercase) is the energy to raise 1 gram of water by 1°C. A kilocalorie (kcal) equals 1,000 calories. Food labels in most countries display kcal, often labelled simply as "Calories" (uppercase).