Kilocalories to Kilojoules
Type a value in either box to convert between kilocalories and kilojoules. The factor is 4.184.
| Kilocalories | Kilojoules |
|---|---|
| 1 kcal | 4.184 kJ |
| 2 kcal | 8.368 kJ |
| 3 kcal | 12.552 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 |
How to use
- Enter a value in the Kilocalories field.
- The Kilojoules figure appears immediately — no button to press.
- Typing in the Kilojoules field converts back to Kilocalories the same way.
- Use the reference table for the values that come up most often.
Kilocalories to Kilojoules formula
The factor from kilocalories to kilojoules is 4.184.
kJ = kcal × 4.184
Put another way, one kilocalorie is exactly 523/125 kilojoules.
Why this factor: the kilocalorie and the kilojoule are both defined against the joule, so dividing one definition by the other gives 4.184 directly. Both definitions are set out in full below.
To go the other way, divide by 4.184 — or use the Kilojoules to Kilocalories converter, which is the same calculation reversed.
Worked example
Take 500 kcal and multiply by the factor 4.184: the result is 2092 kJ.
500 kcal × 4.184 = 2092 kJ
The converter above does this for any value you type, in either direction.
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.
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.
Kilocalories vs Kilojoules
The kilocalorie is a specialized unit while the kilojoule is a metric 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 kilojoules are in a kilocalorie?
One kilocalorie equals 4.184 kilojoules.
What is the formula to convert kilocalories to kilojoules?
Multiply the number of kilocalories by 4.184. To reverse it, divide by 4.184 instead.
How do I convert kilojoules back to kilocalories?
Divide by 4.184, which is the same as multiplying by 0.239005736.
How many kilojoules are in 10 kilocalories?
10 kcal works out to 41.84 kJ.
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 kilocalorie defined?
Exactly 4,184 joules.