Quick Answer
1 kilocalorie (kcal) = 4.184 kilojoules (kJ), and 1 kilojoule = 0.239006 kilocalories. Kilocalories is the larger unit, so the same physical amount needs a bigger number when measured in Kilojoules. Convert either way with the live tool below or the dedicated converter pages.
Key Facts
- 1 kilocalorie (kcal) = 4.184 kJ
- 1 kilojoule (kJ) = 0.239006 kcal
- Conversion is exact multiplication - no rounding in the factor
- Table below covers common values in both directions
- Dedicated converters: kcal→kJ and kJ→kcal pages with live tools
Frequently Asked Questions
Which is bigger, a kilocalorie or a kilojoule?
One kilocalorie equals 4.184 kJ, and one kilojoule equals 0.239006 kcal. The unit with the larger factor is the physically bigger one.
How do I convert kilocalories to kilojoules?
Multiply by the factor: value in kJ = value in kcal × 4.184. Example: 5 kcal = 20.92 kJ. Reverse: divide by 4.184 (or multiply by 0.239006).
Why are kilocalories and kilojoules different?
They are two different units measuring the same physical quantity. A kilocalorie is defined as exactly 4.184 kJ, and a kilojoule as exactly 0.239006 kcal. Because the units differ in size, the number you write down for the same amount depends on which unit you use - the conversion factor itself is exact, with no rounding.
Is there a quick way to convert without a calculator?
Memorize the 1-to factor: 1 kilocalorie ≈ 4.184 kJ. Then multiply. For 2 kcal that's ≈ 8.368 kJ.