How to convert kilocalories to kilojoules
To convert a measurement in kilocalories to kilojoules, multiply the value by 4.184. The conversion factor comes from the relationship between both units and the joule.
For example, to convert 5 kcal to kilojoules: 5 × 4.184 = 20.92 kJ.
What is a kilocalorie?
A kilocalorie equals 1,000 small calories, or exactly 4,184 joules, and is the 'Calorie' shown on food nutrition labels. The food Calorie (capital C) is actually a kilocalorie. This convention, established in nutrition science, means a 500-Calorie meal contains 500 kilocalories, or about 2,092 kilojoules.
Common uses of kilocalories include: Food energy (the dietary 'Calorie'); Metabolism and exercise burn estimates; Nutrition and diet planning; Bomb-calorimetry food testing.
What is a kilojoule?
A kilojoule equals 1,000 joules and is the standard metric unit for expressing food energy on nutrition labels in most of the world. As metric countries adopted SI units for food labeling, the kilojoule replaced the food calorie on packaging in regions such as Australia, New Zealand, and the European Union (shown alongside kcal).
Common uses of kilojoules include: Food energy on nutrition labels; Dietary and exercise energy tracking; Chemical reaction energy (enthalpy); Battery and mechanical energy specs.
When you need to convert kilocalories to kilojoules
This is the everyday nutrition conversion. Food labels in the United States show kilocalories (the 'Calories' you count), while Australia, New Zealand, and the EU show kilojoules. Converting a 250 kcal snack to about 1,046 kJ lets you compare packaging across regions and track intake consistently.
Kilocalories to kilojoules worked examples
Here are some common values converted:
1 kcal = 4.184 kJ 5 kcal = 20.92 kJ 10 kcal = 41.84 kJ 50 kcal = 209.2 kJ 100 kcal = 418.4 kJ
Frequently asked questions
How many kilojoules are in one kilocalorie?
One kilocalorie (kcal) equals 4.184 kilojoules (kJ). Multiply any value in kilocalories by 4.184 to convert to kilojoules.
How do I convert kilocalories to kilojoules?
Multiply the value in kilocalories by 4.184. For example, 5 kcal × 4.184 = 20.92 kJ.
How do I convert kilojoules to kilocalories?
Multiply the value in kilojoules by 0.239005736138, or divide by 4.184. Use the swap button on the converter above to reverse the direction.
Is the kilocalorie to kilojoule conversion exact?
The thermochemical calorie is defined as exactly 4.184 J and the BTU as 1055.056 J. Conversions between SI energy units are exact.
What is the formula for kilocalories to kilojoules?
The formula is: kJ = kcal × 4.184. This comes from the definition of both units relative to the joule.