Energy Converter

Convert energy between joules, calories, kilowatt-hours, BTU, electronvolts and other units used in food, electricity, heating and physics.

How to use the Energy Converter

  1. Type the value you want to convert in the first box.
  2. Choose the unit you are converting from and the unit you want to convert to.
  3. Read the result instantly. Use the swap button to reverse the direction, or copy the result with one click.

Popular energy conversions

ConversionResultFormula
Kilocalories to kilojoules1 kcal = 4.184 kJkilojoules = kilocalories × 4.184
Kilojoules to kilocalories1 kJ = 0.239006 kcalkilocalories = kilojoules ÷ 4.184
Joules to calories1 J = 0.239006 calcalories = joules ÷ 4.184
Calories to joules1 cal = 4.184 Jjoules = calories × 4.184
Kilowatt-hours to joules1 kWh = 3,600,000 Jjoules = kilowatt-hours × 3,600,000
Joules to kilowatt-hours1 J = 0.000000277778 kWhkilowatt-hours = joules ÷ 3,600,000
British thermal units to kilowatt-hours1 BTU = 0.000293071 kWhkilowatt-hours = British thermal units × 0.00029307107
Kilowatt-hours to British thermal units1 kWh = 3,412.14 BTUBritish thermal units = kilowatt-hours × 3,412.1416
Kilojoules to joules1 kJ = 1,000 Jjoules = kilojoules × 1,000
Joules to kilojoules1 J = 0.001 kJkilojoules = joules ÷ 1,000
Kilowatt-hours to megajoules1 kWh = 3.6 MJmegajoules = kilowatt-hours × 3.6
Megajoules to kilowatt-hours1 MJ = 0.277778 kWhkilowatt-hours = megajoules ÷ 3.6
British thermal units to joules1 BTU = 1,055.06 Jjoules = British thermal units × 1,055.0559
Joules to British thermal units1 J = 0.000947817 BTUBritish thermal units = joules × 0.00094781712
Electronvolts to joules1 eV = 1.6022 × 10-19 Jjoules = electronvolts × 1.6022 × 10<sup>-19</sup>
Joules to electronvolts1 J = 6.2415 × 1018 eVelectronvolts = joules × 6.2415 × 10<sup>18</sup>
Kilocalories to calories1 kcal = 1,000 calcalories = kilocalories × 1,000
Calories to kilocalories1 cal = 0.001 kcalkilocalories = calories ÷ 1,000
Watt-hours to joules1 Wh = 3,600 Jjoules = watt-hours × 3,600
Joules to watt-hours1 J = 0.000277778 Whwatt-hours = joules ÷ 3,600
Kilowatt-hours to kilocalories1 kWh = 860.421 kcalkilocalories = kilowatt-hours × 860.42065
Kilocalories to kilowatt-hours1 kcal = 0.00116222 kWhkilowatt-hours = kilocalories × 0.0011622222

Supported energy units

UnitSymbolEqual to
JouleJ1 J
KilojoulekJ1,000 J
MegajouleMJ1,000,000 J
GigajouleGJ1,000,000,000 J
Caloriecal4.184 J
Kilocalorie (food Calorie)kcal4,184 J
Watt-hourWh3,600 J
Kilowatt-hourkWh3,600,000 J
Megawatt-hourMWh3,600,000,000 J
British thermal unitBTU1,055.0559 J
Therm (US)thm105,480,400 J
Foot-poundft·lbf1.3558179 J
ElectronvolteV1.6022 × 10-19 J
KiloelectronvoltkeV1.6022 × 10-16 J
MegaelectronvoltMeV1.6022 × 10-13 J
Ergerg0.0000001 J
Ton of TNTtTNT4,184,000,000 J
Tonne of oil equivalenttoe41,868,000,000 J

Energy units in everyday life

The joule is the SI unit of energy. It is small: lifting an apple one meter takes about one joule. That is why food labels use kilojoules or kilocalories and electricity bills use kilowatt-hours.

  • Food: the “Calorie” on a label is a kilocalorie. 1 kcal = 4.184 kJ.
  • Electricity: 1 kWh is the energy used by a 1,000 W appliance in one hour, equal to 3.6 MJ.
  • Heating and cooling: 1 BTU is about 1,055 J; natural gas is billed in therms (100,000 BTU).
  • Physics: the electronvolt is the energy gained by one electron moving through one volt.

This converter uses the thermochemical calorie (4.184 J) and the International Table BTU (1,055.056 J).

Frequently asked questions

How many joules are in a calorie?

One thermochemical calorie is exactly 4.184 joules. One food Calorie (kilocalorie) is 4,184 joules.

How do I convert kcal to kJ?

Multiply kilocalories by 4.184. For example, 500 kcal is 2,092 kJ.

How many joules are in a kilowatt-hour?

One kilowatt-hour is exactly 3,600,000 joules (3.6 MJ).

How many BTU are in a kWh?

One kilowatt-hour is about 3,412.14 BTU.

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