Energy Converter
Convert energy, work, and heat between SI metric units (Joules, kilojoules, megajoules), electricity billing metrics (kilowatt-hours, watt-hours), dietary units (calories, food kcal), and thermal units (BTU).
1 kWh = 3.6 MJ
1 kWh = 3.6 MJ
Common Conversions
1 kWh =3,600,000 J
1 kWh =3,600 kJ
1 kWh =3.6 MJ
1 kWh =1,000 Wh
1 kWh =860,420.6501 cal
How Energy Conversions Work
In physics, energy is the quantitative property transferred to a body to perform work or heat. The coherent SI unit of energy is the Joule (J), equal to one watt applied over one second (1 W·s) or one Newton applied over one meter (1 N·m):
1 Joule (J) = 1 N·m = 1 W·s
1 Kilojoule (kJ) = 1,000 J
1 Megajoule (MJ) = 1,000,000 J = 10&sup6; J
1 Watt-hour (Wh) = 3,600 J
1 Kilowatt-hour (kWh) = 3,600,000 J = 3.6 MJ
1 Thermochemical Calorie (cal) = 4.184 J
1 Food Calorie (kcal / Cal) = 1,000 cal = 4,184 J
1 British Thermal Unit (BTU) ≈ 1,055.056 J
Dietary Calories vs. Scientific Calories
A major point of confusion in nutrition and consumer health is the difference between a scientific small calorie and a dietary food Calorie:
- Small Calorie (cal, gram calorie): The energy required to raise the temperature of 1 gram of water by 1°C (defined in the thermochemical standard as exactly 4.184 J).
- Food Calorie (kcal, large Calorie, Cal): Nutrition facts labels in the United States and worldwide display "Calories" with a capital 'C' or "kcal". One food Calorie is equal to 1,000 small calories (4,184 J or 4.184 kJ).
When a snack reports 250 Calories, it contains 250 kcal = 250,000 small calories = 1,046,000 Joules (approx. 1.05 MJ).
Official Energy Conversion Standards
| Unit | Symbol | Type | Exact Definition in Joules (J) |
|---|---|---|---|
| Joule | J | SI Base Equivalent | 1 J (1 N·m = 1 W·s) |
| Kilojoule | kJ | Metric SI Prefix | 1,000 J (10³ J) |
| Megajoule | MJ | Metric SI Prefix | 1,000,000 J (10&sup6; J) |
| Watt-hour | Wh | Electrical Metric | 3,600 J (1 W × 3,600 s) |
| Kilowatt-hour | kWh | Electric Utility | 3,600,000 J (3.6 MJ) |
| Calorie (Thermochemical) | cal | Scientific Heat | 4.184 J |
| Food Calorie (kcal) | kcal | Nutrition / Diet | 4,184 J (1,000 cal = 4.184 kJ) |
| British Thermal Unit | BTU | HVAC / Thermal | 1,055.05585262 J (ISO / IT standard) |
Common Energy Benchmarks
1 kWh of Electricity
3.6 MJ ≈ 860.4 kcal ≈ 3,412.1 BTU
Air Conditioner (12,000 BTU/h)
12,000 BTU ≈ 12.66 MJ ≈ 3.52 kWh
Daily Dietary Intake (2,000 kcal)
2,000 kcal = 8.368 MJ ≈ 2.32 kWh
Smartphone Battery (15 Wh)
15 Wh = 54,000 J = 54 kJ ≈ 12.9 kcal
Gallon of Gasoline
≈ 120 MJ ≈ 33.3 kWh ≈ 114,000 BTU
1 Joule Physical Equivalent
Lifting a 100 g apple 1 meter upward on Earth