Kilocalories to Joules
An instant kilocalories-to-joules converter, with the formula and a reference table below.
| Kilocalories | Joules |
|---|---|
| 1 kcal | 4184 J |
| 2 kcal | 8368 J |
| 3 kcal | 12552 J |
| 5 kcal | 20920 J |
| 10 kcal | 41840 J |
| 25 kcal | 104600 J |
| 50 kcal | 209200 J |
| 100 kcal | 418400 J |
How to use
- Enter a value in the Kilocalories field.
- The Joules figure appears immediately — no button to press.
- Typing in the Joules field converts back to Kilocalories the same way.
- Use the reference table for the values that come up most often.
Kilocalories to Joules formula
To convert kilocalories to joules, multiply by 4184.
J = kcal × 4184
Put another way, one kilocalorie is exactly 4,184 joules.
Why this factor: the kilocalorie and the joule are both defined against the joule, so dividing one definition by the other gives 4184 directly. Both definitions are set out in full below.
To go the other way, divide by 4184 — or use the Joules to Kilocalories converter, which is the same calculation reversed.
Worked example
Take 100 kcal and multiply by the factor 4184: the result is 418400 J.
100 kcal × 4184 = 418400 J
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 joule?
The joule is the SI unit of energy — the work done by one newton acting over one meter.
Definition: Defined as 1 N·m, equivalently one watt-second. Named after James Prescott Joule.
Where it is used: All scientific energy calculations, food energy on European labels, and mechanical work.
Kilocalories vs Joules
The kilocalorie is a specialized unit while the joule is an SI 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 joules are in a kilocalorie?
One kilocalorie equals 4184 joules.
What is the formula to convert kilocalories to joules?
Multiply the number of kilocalories by 4184. To reverse it, divide by 4184 instead.
How do I convert joules back to kilocalories?
Divide by 4184, which is the same as multiplying by 0.000239005736.
How many joules are in 10 kilocalories?
10 kcal works out to 41840 J.
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.