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Energy Converter

Convert between joules, calories, BTUs, kilowatt-hours, and more.

13 units
6 decimals

1 J = 0.239006 cal

About the energy converter

Convert energy across SI (joule, kilojoule), thermal (calorie, BTU), electrical (kilowatt-hour), and atomic (electron-volt) units. The SI derived unit is the joule. Different fields use different conventions: nutrition uses kilocalories ("Calories"), HVAC uses BTU, and electricity uses kilowatt-hours.

Frequently asked questions

  • How many joules are in a calorie?

    One thermochemical calorie equals exactly 4.184 joules.

  • How many joules are in 1 kilowatt-hour?

    One kWh equals 3,600,000 J (3.6 MJ).

  • Are nutrition Calories the same as calories?

    Nutritional Calories (capital C) are kilocalories — 1,000 small calories. So a 200-Calorie snack contains 200,000 calories of energy.

  • What is the SI unit of energy?

    The joule (J), equal to one newton-meter or one watt-second.

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Complete list of energy units