1. How to convert kcal to kJ
The conversion is a single multiplication: kJ = kcal × 4.184. Both units are defined
against the same base — the joule (J) — so the factor is fixed and the result
is exact to the precision shown.
Worked at the two values people ask for most: 1 kcal = 4.184 kJ and
100 kcal = 418.4 kJ. Going the other way, kcal = kJ × 0.239005736138, so
1 kJ = 0.23900574 kcal — a direction with its own page, kJ to kcal.
Results are given to eight significant figures. That is more precision than most jobs need — for a rough figure, use 1 kcal = 4.184 kJ and adjust — but rounding early and multiplying afterwards is how a small error becomes a visible one, so the full figure is what the converter carries.
2. Kilocalories to Kilojoules conversion table
| Kilocalories (food calories) (kcal) | Kilojoules (kJ) |
|---|---|
| 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 |
| 250 kcal | 1,046 kJ |
| 500 kcal | 2,092 kJ |
| 1,000 kcal | 4,184 kJ |
Every row is the same factor applied — nothing in the table is a special case, and any value in between behaves the same way. Type your own figure into the converter above and the Formula tile shows the arithmetic being used, so the result is checkable rather than taken on trust.
3. What the two units are
- Kilocalories (food calories) (kcal). One kcal is 4,184 J.
- Kilojoules (kJ). One kJ is 1,000 J.
Both are converted through the joule (J): the value is multiplied by its own unit's factor to reach the base, then divided by the target unit's factor to leave it. No direct kcal to kJ factor has to exist or be kept correct, which is also why the converter can show the same value in all 10 energy units at once.
The calorie is two units: the food Calorie is a kilocalorie, and the physics calorie is a thousandth of it. This category uses kcal and kJ, the pair printed on nutrition labels, where 1 kcal is exactly 4.184 kJ by the thermochemical definition. A kilowatt-hour is exactly 3.6 MJ.
If the pair you actually want is not this one, the full unit converter runs every 10 energy units off the same factor table, along with 11 other categories of measurement.
4. Kilocalories to Kilojoules FAQs
How do I convert kcal to kJ?
Multiply by 4.184. 1 kcal = 4.184 kJ, and 100 kcal = 418.4 kJ. The factor is exact to the precision shown, so the only rounding is the one you choose to do at the end.
How many kJ is 1 kcal?
1 kcal = 4.184 kJ. The full formula is kJ = kcal × 4.184, and 1 kJ = 0.23900574 kcal going the other way.
What is 100 kcal in kJ?
100 kcal = 418.4 kJ. The table above works the same factor through 10 values, and the converter takes any figure you type — including decimals.
How do I convert kJ to kcal?
kcal = kJ × 0.239005736138, so 1 kJ = 0.23900574 kcal. Use the Swap button in the converter to reverse the direction without retyping the value, or open the dedicated kJ to kcal page.
Which calorie does this use?
The kilocalorie — the food Calorie, exactly 4.184 kJ by the thermochemical definition. The physics calorie is a thousandth of it, and both appear in the converter. A kilowatt-hour is exactly 3.6 MJ.
Is anything I type sent to a server?
No. The factor table ships with the page and every conversion runs in your browser. Nothing is uploaded, logged or written to storage, and the converter keeps working offline once the page has loaded.