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Energy Converter

Convert energy units instantly

Convert between joules, kilojoules, calories, kilocalories, watt-hours, kWh, eV, BTU and foot-pounds - instantly as you type

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About the energy converter

The energy converter translates between the most common units of energy and work, from joules and calories to kilowatt-hours, electronvolts, and BTU. Type any amount, choose the unit you are converting from and the unit you want, and the result updates live as you type. Use the swap button to reverse the direction in a single click.

All conversions run through the joule, the SI unit of energy. Standard factors are used: 1 cal = 4.184 J, 1 Wh = 3600 J, 1 kWh = 3.6 MJ, 1 BTU = 1055.06 J, and 1 eV = 1.602 × 10⁻¹⁹ J.

Supported units

  • J, kJ, cal, kcal
  • Wh, kWh, eV, BTU, ft·lb

How to use the energy converter

  1. Enter a value

    Type the energy amount you want to convert.

  2. Pick the from and to units

    Select the unit you are converting from and the unit you want to convert to.

  3. Swap if needed

    Use the swap button to reverse the conversion direction instantly.

Frequently asked questions

Are the conversions accurate?
Yes. All units are converted through the joule using standard, internationally recognized factors such as 1 cal = 4.184 J and 1 kWh = 3.6 MJ.
What is the difference between calories and kilocalories?
One kilocalorie (kcal) equals 1000 calories. In food labeling, the "Calorie" written with a capital C is actually one kilocalorie.
How do I convert kWh to joules?
One kilowatt-hour equals 3.6 million joules (3.6 MJ). The converter applies this factor automatically when you switch between kWh and J.
Does it work offline?
The converter runs entirely in your browser, so once the page is loaded it works without an internet connection.
Is the energy converter free?
Yes, it is completely free and requires no account or sign-up.

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