Kcal to kJ Converter (and kJ to kcal)

kcal to kJ formula

In nutrition, energy is often given either in kilocalories (kcal, also written as Calories) or in kilojoules (kJ). The exact physical relationship is:

To convert from kilocalories to kilojoules, multiply by 4.184:

kJ to kcal formula

To go the other way (from kilojoules to kilocalories), divide by 4.184:

Worked examples

Example 1 – 100 kcal to kJ

Suppose a snack bar has 100 kcal and you want to know the energy in kJ:

Rounded to whole kilojoules (as many labels do): 418 kJ.

Example 2 – 500 kJ to kcal

A drink label shows 500 kJ. Convert to kcal:

Rounded to whole kcal: 120 kcal.

kcal vs kJ on nutrition labels

Different countries prefer different units for food energy:

• United States & many others: Calories (kcal) are standard.
• European Union, Australia, New Zealand: kJ are mandatory; kcal are often shown in brackets.

On labels, “Calories” with a capital C are actually kilocalories (kcal). Our converter uses this nutrition convention: 1 Calorie = 1 kcal = 4.184 kJ.

Typical daily intake in kcal and kJ

Common guideline intakes and their equivalents:

FAQ: kcal and kJ

Is 1 kcal the same as 1 Calorie?

Yes. In nutrition, 1 Calorie (with a capital C) is defined as 1 kilocalorie (kcal). Both equal 4.184 kilojoules (kJ).

Why do some apps use kJ instead of kcal?

Apps targeting regions where regulations require kJ (for example the EU or Australia) often default to kilojoules. Many allow you to switch between kJ and kcal; this converter lets you do the same instantly.

How precise is the 4.184 factor?

1 kcal is exactly 4.184 kJ by definition. For everyday nutrition tracking, rounding to 4.18 or even 4.2 is usually fine, but our calculator uses the exact factor and lets you choose how many decimals to display.