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Calories to Kilojoules
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Calories to Kilojoules — quick reference

1 kcal = 4.184 kj
Common Calories to Kilojoules conversions
kcal kj
1 kcal 4.184 kj
2 kcal 8.368 kj
3 kcal 12.552 kj
5 kcal 20.92 kj
10 kcal 41.84 kj
20 kcal 83.68 kj
25 kcal 104.6 kj
50 kcal 209.2 kj
100 kcal 418.4 kj
250 kcal 1046 kj
500 kcal 2092 kj
1000 kcal 4184 kj
// about this tool

Calories to Kilojoules Online

Updated 2026-10-24

Convert Calories to kilojoules online for free. Enter a (dietary) Calorie value and SnapTools shows the exact value in kJ instantly, in your browser. Nothing is uploaded.

US and UK food labels list energy in Calories; the EU, Australia, and many other regions require kilojoules, so a "100 Calorie" snack pack needs converting to mean anything on a kJ-labelled product. This tool works in dietary Calories (kilocalories), not the much smaller chemistry "calorie", using the exact 4.184 kJ factor. For the full family of energy units (joules, watt-hours, BTU), use the Energy Converter.

// how to use

  1. 1 Type or paste an energy value in (dietary) Calories into the input.
  2. 2 SnapTools converts it to kilojoules as you type.
  3. 3 Copy the result, or use the slider for a quick scrub across common food-label values.

// examples

A 100-calorie snack
Input
100
Output
418.4 kJ
A 2,000-calorie daily reference
Input
2000
Output
8368 kJ

// common uses

Converting a US/UK food label's Calorie count to the kJ figure required elsewhere Checking a fitness app's calorie burn against a kJ-based target Comparing nutrition labels between regions Checking a manual energy conversion

// faq

Who invented the calorie as a unit of measurement?
French chemist Nicolas Clement introduced the calorie in the early 1820s while lecturing on heat and calorimetry. It did not become a familiar food-energy term until the 1890s, when nutrition scientist Wilbur Olin Atwater used it to popularize the Calorie figures still printed on labels today.
Are food-label "Calories" the same as this tool's kilocalories?
Yes. The dietary "Calorie" (capital C) on a food label is a kilocalorie (kcal), 1,000 times the small "calorie" used in chemistry. This tool converts the dietary/food-label figure.
Why do some food labels show both kJ and Calories?
Many countries (EU, Australia, and others) legally require energy in kilojoules on nutrition labels, while US/UK labels traditionally use Calories, so a food imported between regions often needs the other unit.
What's the exact conversion factor?
1 kilocalorie (dietary Calorie) is exactly 4.184 kilojoules. This tool uses that exact figure.
What about converting kilojoules back to Calories?
Use Kilojoules to Calories, or the full Energy Converter for joules, watt-hours, and BTU.

// works with your data

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Use this via API

Get a free API key → 
curl -X POST https://thesnaptools.com/api/v1/tools/calories-to-kilojoules \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"value":"100"}'