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Energy
Kilocalories to Kilojoules
Convert kilocalories (kcal) to kilojoules (kJ). Type a value below to see the result update instantly. Reference table and formula included.
Calculator
1 kcal = 4.184 kJ
Kilocalories to Kilojoules Conversion Table
Common values, ready to copy:
| kilocalories | kilojoules |
|---|---|
| 1 kcal | 4.184 kJ |
| 2 kcal | 8.368 kJ |
| 5 kcal | 20.92 kJ |
| 10 kcal | 41.84 kJ |
| 25 kcal | 104.6 kJ |
| 50 kcal | 209.2 kJ |
| 100 kcal | 418.4 kJ |
| 1,000 kcal | 4184 kJ |
Formula
kilojoules = kilocalories × 4.184
Energy uses the SI joule. Food calories (kcal) are 1,000 small calories: 1 kcal = 4,184 J. 1 kWh = 3.6 MJ = 3,600,000 J. 1 BTU = 1,055.06 J.
About Kilocalories and Kilojoules
Kilocalories (kcal): A thousand small calories, or about 4,184 J; this is what 'calories' means on US food labels. Common uses: Food energy labeling in the US (a 'Calorie' on a US food label is a kilocalorie), nutrition tracking, and exercise energy expenditure.
Kilojoules (kJ): A thousand joules; the practical SI energy unit for food and nutrition in metric countries. Common uses: Food energy labeling outside the US, electrical energy in kJ for small batteries, and biology (metabolism).
How the conversion works
Energy uses the SI joule. Food calories (kcal) are 1,000 small calories: 1 kcal = 4,184 J. 1 kWh = 3.6 MJ = 3,600,000 J. 1 BTU = 1,055.06 J.
The exact relationship is kilojoules = kilocalories × 4.184, which the calculator at the top of this page applies in both directions. Type into either field and the other updates immediately.
When this conversion matters
Converting between kilocalories and kilojoules comes up wherever energy measurements move between systems — from one country's conventions to another's, from a scientific reference to a practical specification, or from one industry's working unit to another's. The calculator and reference table above cover the everyday range; for unusual values you can type any number into either field.