Kilojoules to Calories
Type a value in either box to convert between kilojoules and calories. The factor is 239.006.
| Kilojoules | Calories |
|---|---|
| 1 kJ | 239.005736 cal |
| 2 kJ | 478.011472 cal |
| 3 kJ | 717.017208 cal |
| 5 kJ | 1195.028681 cal |
| 10 kJ | 2390.057361 cal |
| 25 kJ | 5975.143403 cal |
| 50 kJ | 11950.286807 cal |
| 100 kJ | 23900.573614 cal |
How to use
- Enter a value in the Kilojoules field.
- The Calories figure appears immediately — no button to press.
- Typing in the Calories field converts back to Kilojoules the same way.
- Use the reference table for the values that come up most often.
Kilojoules to Calories formula
The factor from kilojoules to calories is 239.005736.
cal = kJ × 239.005736
Why this factor: the kilojoule and the calorie are both defined against the joule, so dividing one definition by the other gives 239.005736 directly. Both definitions are set out in full below.
To go the other way, divide by 239.005736 — or use the Calories to Kilojoules converter, which is the same calculation reversed.
Worked example
Take 500 kJ and multiply by the factor 239.005736: the result is 119502.868069 cal.
500 kJ × 239.005736 = 119502.868069 cal
The converter above does this for any value you type, in either direction.
What is a kilojoule?
A kilojoule is 1,000 joules, the metric unit of food energy.
Definition: Exactly 1,000 joules.
Where it is used: Nutrition labels in Europe and Australia, and heating and cooling loads.
What is a calorie?
A calorie is the energy needed to warm one gram of water by one degree Celsius.
Definition: The thermochemical calorie is defined as exactly 4.184 joules.
Where it is used: Chemistry and physics literature, and older engineering references.
Worth knowing: The 'calories' on a nutrition label are actually kilocalories — 1,000 of these. A 500-Calorie meal is 500 kcal, or about 2.1 million joules.
Kilojoules vs Calories
The kilojoule is a metric unit while the calorie is a specialized unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many calories are in a kilojoule?
One kilojoule equals 239.005736 calories.
What is the formula to convert kilojoules to calories?
Multiply the number of kilojoules by 239.005736. To reverse it, divide by 239.005736 instead.
How do I convert calories back to kilojoules?
Divide by 239.005736, which is the same as multiplying by 0.004184.
How many calories are in 10 kilojoules?
10 kJ works out to 2390.057361 cal.
Is there anything to watch out for with calories?
The 'calories' on a nutrition label are actually kilocalories — 1,000 of these. A 500-Calorie meal is 500 kcal, or about 2.1 million joules.
How is the kilojoule defined?
Exactly 1,000 joules.