Calorie to kJ Converter
Convert food calories (kcal) to kilojoules for European nutrition labels, fitness tracking and diet planning. 1 kcal = 4.184 kJ — reference table for common foods.
Last updated: May 2026
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How to use this converter
Calories appear on US nutrition labels, while kilojoules are used on EU, UK and Australian labels. Use this converter when comparing the energy in a food across labels from different regions. kJ = kcal × 4.184
Common reference values
| kcal | kJ |
|---|---|
| 100 | 418.4 |
| 250 | 1046 |
| 500 | 2092 |
| 2000 | 8368 |
Frequently Asked Questions
Why are there different energy units?
Different fields developed different energy measurements historically. Calories are used in nutrition, joules in physics, and kilowatt-hours in electricity. Converting between them is common.
What's the difference between calories and Calories?
A food Calorie (with capital C) is actually 1 kilocalorie (1000 calories with lowercase c). Nutrition labels use kilocalories, which is why food energy seems smaller than expected when converted to other units.
When would I need this conversion?
Nutritionists convert calories, physicists use joules, electricians use kilowatt-hours. Converting between them is necessary when comparing energy across different fields or applications.
Why do US nutrition labels use calories but European labels use kilojoules?
The FDA in the United States mandates calorie labeling on packaged food. Most of the rest of the world—including the EU, UK, Canada, and Australia—requires kilojoule labeling instead. This creates confusion when comparing products across borders. A 100-calorie snack is about 420 kJ; without conversion, European shoppers might think it's four times higher in energy. International brands have to relabel or modify their packaging for different markets.
Does cooking or food prep change the calorie count on the label?
The label shows calories for the food as sold (raw or cooked, depending on the product). Cooking can change water content and some nutrient availability, but the total energy content of the food itself doesn't change. If you weigh food after cooking, you might get a different calorie amount per gram because water evaporates, making it more concentrated. Converting calories to kJ doesn't change this—you need to account for weight changes separately.