Convert energy between joules, kilojoules, calories, kilocalories, watt-hours and kilowatt-hours. The answer updates instantly, with the formula and a table of every unit.
It is handy for nutrition labels (kcal in the US, kJ in Australia and Europe), comparing electricity use in kWh, battery capacities in watt-hours, and physics and chemistry problems.
How to use the Energy Converter tool
- Type the number you want to convert in the Value box, for example 2,000 with kilocalories selected.
- Pick the unit you have in From and the unit you need in To.
- Read the result instantly in large type, with the exact formula used shown underneath.
- Open All energy units to see the same value in every unit at once, or press ⇄ to swap the direction.
- Use Copy result to paste the converted number into a document, spreadsheet or message.
Why use ToolOrca Energy Converter
- Six units for food, heat and power
- Exact: 1 kcal = 4.184 kJ
- kWh for electricity bills
- All units listed together
- Instant live conversion
- Free, private, offline
How energy conversion works
The joule is the SI unit of energy. One thermochemical calorie is exactly 4.184 J, so one kilocalorie, the “Calorie” printed on food labels, is 4,184 J or 4.184 kJ. One watt-hour is one watt for one hour, 3,600 J, and one kilowatt-hour is 3.6 million joules.
Worked example: a 2,000 kcal daily diet is 2,000 × 4.184 = 8,368 kJ, which is 2.32444 kWh.
Frequently asked questions
How many kJ are in a kcal?
One kilocalorie is exactly 4.184 kJ.
Are food Calories the same as calories?
No. A food Calorie (capital C) is a kilocalorie, 1,000 small calories. Nutrition labels that say 250 Calories mean 250 kcal.
How many joules are in a kWh?
One kilowatt-hour is exactly 3,600,000 joules (3.6 MJ).
How many kcal is 1 kWh?
One kWh is 860.421 kcal.