Converting units can be difficult, so when doing so it is important to remember to write down your computations step by step and to label all units. Joules (J) and calories, the derivative units of kilojoules (kJ) and kilocalories (kcal), are both used to measure energy. Keep in mind the prefix kilo (k) means 1,000.
Always label units when doing computations
Write down the initial value in kilojoules (kJ). Take 3 kJ as an example. Each step will conclude with the conversion process for this number.
Multiply the initial value by the conversion factor (1,000 J / 1 kJ). The kJ units will cancel out and leave you with a value in J. Using the example: 3 kJ x (1,000 J / 1 kJ) = 3,000 J.
Multiply the value obtained in Step 2 by the conversion factor (0.239 calories / 1 J). The J units will cancel out and leave you with a value in calories. Continuing with the example: 3,000 J x (0.239 calories / 1 J) = 717 calories.
Multiply the value obtained in Step 3 by the conversion factor (1 kcal / 1,000 calories). The calorie units will cancel out and leave you with your final value in kcal. Finishing out the example: 717 calories x (1 kcal / 1,000 calories) = 0.717 kilocalories.