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kcal to kj Converter

Convert kcal to kJ and back — 1 kcal = 4.184 kJ. Free, instant, no sign-up, full working shown.

Convert kcal ⇄ kJ

418.4 kJ
100 kcal = 418.4 kJ (1 kcal = 4.184 kJ (thermochemical calorie))

Formula: 100 kcal × 4.184 = 418.4 kJ

How the kcal to kj converter conversion works

The converter applies kJ = kcal × 4.184. Going the other way, kcal = kJ ÷ 4.184. The factor is the thermochemical calorie: one kilocalorie is 4.184 kilojoules, the value food labelling uses.

Worked example: a 100 kcal snack is 100 × 4.184 = 418.4 kJ, and a 2000 kcal daily intake is 2000 × 4.184 = 8368 kJ.

UK and EU labels show both units side by side, so a label reading 418 kJ / 100 kcal is one number in two units, not two different amounts. For more everyday tools, see the full list on the homepage.

kcal to kj converter questions

How many kJ are in 100 kcal?
418.4 kJ — 100 × 4.184 = 418.4.
How do I convert kcal to kJ?
Multiply by 4.184: kJ = kcal × 4.184. So 250 kcal is 250 × 4.184 = 1046 kJ.
How do I convert kJ back to kcal?
Divide by 4.184: kcal = kJ ÷ 4.184. So 418.4 kJ is 418.4 ÷ 4.184 = 100 kcal.
Why do food labels show both kcal and kJ?
UK and EU nutrition labels list energy in both units — kilojoules are the SI unit, kilocalories the traditional one — so the same food shows, for example, 418 kJ and 100 kcal side by side.
Are food calories the same as kcal?
Yes. A food Calorie (capital C) is one kilocalorie — 1,000 small calories — which is why a 100 kcal snack is described as 100 calories.

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Sources & official guidance

Estimate only — 1 kcal is 4.184 kJ (thermochemical calorie); label values are rounded by manufacturers. See our disclaimer.