Kilocalories to Kilojoules Converter (kcal to kJ)

The "Calories" on a US nutrition label, in fitness trackers and in most diet books are kilocalories, while Australia and New Zealand label food energy in kilojoules and EU packs show both. A recipe or meal plan written in kcal therefore needs converting before it can be compared with an Australian pack, or entered into an app set to kJ.

This converter uses the thermochemical kilocalorie of exactly 4.184 kJ, the value used for food energy. An older International Table kilocalorie of 4.1868 kJ also exists; the two differ by less than 0.07%, far less than the rounding on any label.

How to use this tool

1. Type a value in the Kilocalorie box to see it in kilojoules, or type in the Kilojoule box to convert the other way.
2. Press ⇄ to swap the two units, or Load example for a typical value.
3. Check the charts below for common values; for other units, open the Energy converter.

Formula

kJ = kcal × 4.184

kcal = kJ ÷ 4.184

Both factors come from exact definitions: 1 kilojoule = 0.239005736138 kilocalories and 1 kilocalorie = 4.184 kilojoules (shown to 12 significant digits).

Example

Two conversions worked with the same factors the converter uses:

500 kcal × 4.184 = 2092 kJ

2000 kJ × 0.239005736138 ≈ 478.011 kcal

Kilocalorie to Kilojoule chart

Common values from kilocalories to kilojoules, rounded to four decimal places.

Kilojoule to Kilocalorie chart

The reverse direction for values people often look up.

Food energy counted in kcal

Quick mental estimate

Multiply by 4, then add 5% of the result: 500 kcal → 2,000 + 100 = 2,100 kJ. The shortcut uses 4.2 per kcal, about 0.4% above 4.184, so it lands within 10 kJ for a 500 kcal meal.

Use the converter or the charts when the exact figure matters.

The two units

Kilocalorie (kcal): A kilocalorie (kcal) is 1,000 calories, exactly 4,184 J in the thermochemical definition used here. It is the "Calorie" printed on food and drink labels.

Kilojoule (kJ): A kilojoule (kJ) is 1,000 joules. Food labels in many countries list energy in kJ alongside kilocalories, with 1 kcal equal to 4.184 kJ.