Kilojoules to Kilocalories
An instant kilojoules-to-kilocalories converter, with the formula and a reference table below.
| Kilojoules | Kilocalories |
|---|---|
| 1 kJ | 0.239006 kcal |
| 2 kJ | 0.478011 kcal |
| 3 kJ | 0.717017 kcal |
| 5 kJ | 1.195029 kcal |
| 10 kJ | 2.390057 kcal |
| 25 kJ | 5.975143 kcal |
| 50 kJ | 11.950287 kcal |
| 100 kJ | 23.900574 kcal |
How to use
- Enter a value in the Kilojoules field.
- The Kilocalories figure appears immediately — no button to press.
- Typing in the Kilocalories field converts back to Kilojoules the same way.
- Use the reference table for the values that come up most often.
Kilojoules to Kilocalories formula
To convert kilojoules to kilocalories, multiply by 0.239005736.
kcal = kJ × 0.239005736
Put another way, one kilojoule is exactly 125/523 kilocalories.
Why this factor: the kilojoule and the kilocalorie are both defined against the joule, so dividing one definition by the other gives 0.239005736 directly. Both definitions are set out in full below.
To go the other way, divide by 0.239005736 — or use the Kilocalories to Kilojoules converter, which is the same calculation reversed.
Worked example
Take 500 kJ and multiply by the factor 0.239005736: the result is 119.502868 kcal.
500 kJ × 0.239005736 = 119.502868 kcal
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 kilocalorie?
A kilocalorie is 1,000 calories, and is what food labeling calls a 'Calorie'.
Definition: Exactly 4,184 joules.
Where it is used: Nutrition and dietary energy in the US and much of the world, and metabolic measurements.
Worth knowing: Written with a capital C ('Calorie') or as 'kcal' on labels. This is the unit meant by everyday talk about counting calories.
Kilojoules vs Kilocalories
The kilojoule is a metric unit while the kilocalorie 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 kilocalories are in a kilojoule?
One kilojoule equals 0.239005736 kilocalories.
What is the formula to convert kilojoules to kilocalories?
Multiply the number of kilojoules by 0.239005736. To reverse it, divide by 0.239005736 instead.
How do I convert kilocalories back to kilojoules?
Divide by 0.239005736, which is the same as multiplying by 4.184.
How many kilocalories are in 10 kilojoules?
10 kJ works out to 2.390057 kcal.
Is there anything to watch out for with kilocalories?
Written with a capital C ('Calorie') or as 'kcal' on labels. This is the unit meant by everyday talk about counting calories.
How is the kilojoule defined?
Exactly 1,000 joules.