Calories to Joules
Convert calories to joules instantly — one calorie is 4.184 joules.
| Calories | Joules |
|---|---|
| 1 cal | 4.184 J |
| 2 cal | 8.368 J |
| 3 cal | 12.552 J |
| 5 cal | 20.92 J |
| 10 cal | 41.84 J |
| 25 cal | 104.6 J |
| 50 cal | 209.2 J |
| 100 cal | 418.4 J |
How to use
- Enter a value in the Calories field.
- The Joules figure appears immediately — no button to press.
- Typing in the Joules field converts back to Calories the same way.
- Use the reference table for the values that come up most often.
Calories to Joules formula
Converting calories to joules is a single multiplication by 4.184.
J = cal × 4.184
Put another way, one calorie is exactly 523/125 joules.
Why this factor: the calorie and the joule 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 Joules to Calories converter, which is the same calculation reversed.
Worked example
Given 2000 cal, multiplying by 4.184 yields 8368 J.
2000 cal × 4.184 = 8368 J
The converter above does this for any value you type, in either direction.
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.
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.
Calories vs Joules
The calorie 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 calorie?
One calorie equals 4.184 joules.
What is the formula to convert calories to joules?
Multiply the number of calories by 4.184. To reverse it, divide by 4.184 instead.
How do I convert joules back to calories?
Divide by 4.184, which is the same as multiplying by 0.239005736.
How many joules are in 10 calories?
10 cal works out to 41.84 J.
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 calorie defined?
The thermochemical calorie is defined as exactly 4.184 joules.