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Convert energy.

Joules to calories, kilowatt-hours to megajoules. The calorie on a food label is the kilocalorie, and both are listed.

Energy

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Every unit at once 16 units

Common energy conversions

Each of these has its own page with the formula, a values table and both directions.

calories to joules cal → J kilojoules to kilocalories kJ → kcal kilowatt hours to joules kWh → J British thermal units to joules BTU → J watt hours to kilowatt hours Wh → kWh electronvolts to joules eV → J

Every energy unit on this page

joule J
The SI unit of energy, equal to the work done by a force of one newton acting over a distance of one metre.
kilojoule kJ
A thousand joules, the everyday metric unit for food energy and machine work.
megajoule MJ
A million joules, used in engineering and power generation.
gigajoule GJ
A billion joules, common in industrial energy measurements.
calorie cal
The thermochemical calorie, defined as 4.184 joules. This is the scientific calorie; the 'Calorie' on food labels is a kilocalorie (1,000 of these).
kilocalorie kcal
1,000 thermochemical calories, also called a food Calorie or kilogram calorie. Nutrition labels use this unit.
watt hour Wh
The energy consumed by one watt of power in one hour, equal to 3,600 joules. Household electricity meters measure consumption in kilowatt-hours.
kilowatt hour kWh
A thousand watt-hours, or 3.6 megajoules. The standard unit for household and industrial electricity consumption.
megawatt hour MWh
A million watt-hours, used in large-scale power generation and grid energy accounting.
electronvolt eV
The energy a single electron gains when accelerated through one volt, fundamental in particle physics and solid-state physics.
British thermal unit BTU
The British thermal unit, defined as the energy needed to raise one pound of water by one degree Fahrenheit. Still used in HVAC and heating systems.
therm thm
100,000 BTU, used in natural gas billing in the United States and the United Kingdom.
foot-pound ft·lbf
The energy exerted by a force of one pound-force acting over a distance of one foot, used in engineering and ballistics.
erg erg
A unit of energy in the CGS system, defined as the work done by one dyne of force over one centimetre. Now largely replaced by the joule.
horsepower hour hp·h
The energy equivalent of one horsepower acting for one hour, used in older engineering specifications.
ton of TNT tTNT
The energy released by detonating one metric ton of TNT, used to describe the explosive yield of weapons and natural events.
Other converters
Length Weight and mass Temperature Volume Area Speed Time Data storage Cooking volume Pressure Power Force Angle Frequency Data transfer rate Fuel consumption

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