Energy Converter — kJ to kcal
Convert kilojoules to kilocalories and back — plus joules, megajoules, calories, Wh, kWh and BTU in one place.
About this tool
Enter an amount of energy, choose the unit you have and the unit you want. You get the exact conversion and the same energy in every unit at once — handy for food labels (kJ and kcal), electricity (kWh) and heating (MJ, BTU). Uses the exact definitions: 1 kcal = 4.184 kJ, 1 kWh = 3.6 MJ and 1 BTU = 1,055.06 J.
Frequently asked questions
Divide by 4.184, because 1 kcal = 4.184 kJ (the factor FAO uses for food energy). So 1,000 kJ = 239 kcal, and a food label showing 1,500 kJ per 100 g is 358.5 kcal. To go the other way, multiply kcal by 4.184: 2,000 kcal = 8,368 kJ.
Yes. On food labels and in diet apps, “Calories” (often with a capital C) means kilocalories. One kilocalorie is 1,000 small calories (cal), so a 250 kcal snack is 250,000 cal. Labels in the EU and the UK give the energy in both kJ and kcal.
One kilowatt-hour is exactly 3.6 MJ, which is 860.4 kcal or 3,412 BTU. Turned around, the 2,000 kcal a day often used as a reference intake is about 2.32 kWh of energy.
The thermochemical calorie, 4.184 J, which is the one used for food energy. The International Table calorie used in some engineering tables is 4.1868 J, about 0.07% larger — a difference that only matters for precise technical work.
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