Energy Converter - Convert Energy Units
Convert joules, kilojoules, megajoules, watt-hours, kilowatt-hours, megawatt-hours, calories, kilocalories, British thermal units, and foot-pounds force.
What Is Energy?
Energy is the capacity to do work or transfer heat. The SI unit is the joule (J). Kilojoules (kJ) and megajoules (MJ) are larger SI scales. Electrical energy is commonly billed in watt-hours (Wh), kilowatt-hours (kWh), and megawatt-hours (MWh). Food energy uses calories (cal) and kilocalories (kcal). Heating and cooling often use the British thermal unit (BTU). Mechanical work in customary units is often given as foot-pound force (ft·lbf).
Energy vs Power
Energy is a quantity of work or heat, measured in units such as J, Wh, and kWh. Power is the rate of energy use, measured in watts (W) or kilowatts (kW). This tool converts energy units only. It does not convert power units.
How to Use This Converter
- Enter a non-negative energy value — Changing the value does not update the displayed result yet.
- Select From — Choose the unit of the value you entered. The displayed result stays unchanged until you convert.
- Select To — Choose the unit you want to convert to. The displayed result still waits for Convert.
- Click Convert or press Enter — Calculate the result.
- Swap — Reverse the From and To units and convert using the current value.
- Copy Result — Copy the currently displayed conversion result.
- Reset — Restore the default 1 joule to kilojoule conversion.
Energy Unit Conversion Table
All factors below are the same values used by the converter. Calories use the thermochemical calorie (1 cal = 4.184 J). BTU uses the International Table BTU.
| Group | Unit | Abbreviation | Conversion to joules |
|---|---|---|---|
| Metric / SI | Joule | J | 1 J |
| Metric / SI | Kilojoule | kJ | 1,000 J |
| Metric / SI | Megajoule | MJ | 1,000,000 J |
| Electrical energy | Watt-hour | Wh | 3,600 J |
| Electrical energy | Kilowatt-hour | kWh | 3,600,000 J |
| Electrical energy | Megawatt-hour | MWh | 3,600,000,000 J |
| Heat / food | Calorie (thermochemical) | cal | 4.184 J |
| Heat / food | Kilocalorie (food Calorie) | kcal | 4,184 J |
| Imperial / customary | British thermal unit (IT) | BTU | 1055.05585262 J |
| Imperial / customary | Foot-pound force | ft·lbf | 1.3558179483314004 J |
Practical Uses
- Nutrition: Convert food energy between calories, kilocalories, and kilojoules.
- Electricity: Convert consumption between Wh, kWh, and MWh.
- Heating and cooling: Convert BTUs to joules or kilowatt-hours.
- Mechanical work: Convert foot-pounds force to joules.
- Science and engineering: Move between J, kJ, and MJ.
Common Energy Conversions
| From | To | Conversion |
|---|---|---|
| 1 kilojoule | joules | 1000 J |
| 1 megajoule | joules | 1000000 J |
| 1 watt-hour | joules | 3600 J |
| 1 kilowatt-hour | joules | 3600000 J |
| 1 megawatt-hour | joules | 3600000000 J |
| 1 calorie | joules | 4.184 J |
| 1 kilocalorie | kilojoules | 4.184 kJ |
| 1 British thermal unit | joules | 1055.05585262 J |
| 1 foot-pound force | joules | 1.3558179483314004 J |
Frequently Asked Questions
What energy units can I convert?
This converter supports joules (J), kilojoules (kJ), megajoules (MJ), watt-hours (Wh), kilowatt-hours (kWh), megawatt-hours (MWh), calories (cal), kilocalories (kcal), British thermal units (BTU), and foot-pounds force (ft·lbf).
What is the difference between J, kJ, and MJ?
They are SI energy units on a thousand-fold scale. 1 kJ = 1000 J, and 1 MJ = 1000 kJ = 1,000,000 J.
What is the difference between Wh, kWh, and MWh?
They measure electrical energy. 1 kWh = 1000 Wh = 3,600,000 J. 1 MWh = 1000 kWh = 3,600,000,000 J. A watt (W) is power, not energy.
What is the difference between calories and kilocalories?
1 kcal = 1000 cal. Food labels that say "Calorie" (capital C) usually mean 1 kilocalorie. This converter uses the thermochemical calorie: 1 cal = 4.184 J, so 1 kcal = 4184 J.
What is a BTU?
A British thermal unit is a customary unit of heat energy, widely used in heating and cooling. This converter uses the International Table BTU: 1 BTU = 1055.05585262 J.
What is a foot-pound force?
A foot-pound force (ft·lbf) is the work done by one pound-force acting through one foot. This converter uses 1 ft·lbf = 1.3558179483314004 J.
Does this converter convert power?
No. Energy uses units such as J, Wh, and kWh. Power uses W and kW. This page converts energy units only.