Energy Converter
Convert between units of energy instantly with precise reference factors.
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
1 Joules = 0.001 Kilojoules
This tool provides general unit conversions for everyday and educational use. For regulated, legal, or scientific applications, verify conversion factors against the applicable official standard.
About the Energy Converter
The energy converter switches between joules, kilojoules, calories, kilocalories, watt-hours and kilowatt-hours. It converts through the joule using the thermochemical calorie (1 cal = 4.184 J). The food “Calorie” on nutrition labels is a kilocalorie, which is why a 500-kcal meal is 2,092 kJ. Electricity is billed in kilowatt-hours, and 1 kWh equals 3.6 million joules.
How to use it
- 1Type the value you want to convert.
- 2Choose the unit you are converting from and the unit you want (for example kilocalories to kilojoules).
- 3The result updates as you type; use the swap button to reverse the direction.
- 4Copy or share the result with the buttons below it.
Worked example
500 kcal × 4.184 = 2,092 kJ. One kilowatt-hour is 3,600,000 J, or about 860 kcal.
How it works
How it works
Values are converted through a common base unit for accurate results.
Common use cases
- Converting food energy between kcal and kJ
- Relating electricity use in kWh to joules
- Physics and chemistry homework
Frequently asked questions
A:Conversions use standard reference factors and display up to six significant digits.
A:Yes, use the swap button between the From and To selectors.
Reviewed for accuracy · Last updated October 7, 2026
Conversion factors are based on internationally defined SI units and standard metric/imperial equivalence tables.
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards
References & sources
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