Instantly convert joules, calories, kilowatt-hours and more
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Need to convert joules to kilowatt-hours or calories to kilojoules? This free energy converter handles all common energy units — J, kJ, cal, kcal, Wh, and kWh — in one place. Enter any value, pick your source unit, and get precise conversions instantly. Useful for physics homework, nutrition tracking, electricity billing, and engineering calculations.
One kilowatt-hour (kWh) equals exactly 3,600,000 joules (3.6 MJ). This is the standard unit used on electricity bills, representing the energy consumed by a 1,000-watt device running for one hour.
A kilocalorie (kcal) equals 1,000 thermochemical calories. Food labels use 'Calories' (capital C) to mean kilocalories, so a 200 Calorie snack contains 200 kcal or 836,800 joules.
Multiply kilowatt-hours by 3,600 to get kilojoules. For example, 2 kWh = 7,200 kJ. This follows from the definition: 1 kWh = 3,600 kJ = 3,600,000 J.
There are several definitions of 'calorie'. This tool uses the thermochemical calorie (cal_th = 4.184 J), the most common in chemistry and physics. Nutritional food calories are kilocalories (kcal), also shown separately in the converter.