Joules to Calories
Convert joules to calories instantly — one joule is 0.239006 calories.
| Joules | Calories |
|---|---|
| 1 J | 0.239006 cal |
| 2 J | 0.478011 cal |
| 3 J | 0.717017 cal |
| 5 J | 1.195029 cal |
| 10 J | 2.390057 cal |
| 25 J | 5.975143 cal |
| 50 J | 11.950287 cal |
| 100 J | 23.900574 cal |
How to use
- Enter a value in the Joules field.
- The Calories figure appears immediately — no button to press.
- Typing in the Calories field converts back to Joules the same way.
- Use the reference table for the values that come up most often.
Joules to Calories formula
To convert joules to calories, multiply by 0.239005736.
cal = J × 0.239005736
Put another way, one joule is exactly 125/523 calories.
Why this factor: the joule and the calorie 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 Calories to Joules converter, which is the same calculation reversed.
Worked example
Given 2000 J, multiplying by 0.239005736 yields 478.011472 cal.
2000 J × 0.239005736 = 478.011472 cal
The converter above does this for any value you type, in either direction.
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.
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.
Joules vs Calories
The joule is an SI 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 joule?
One joule equals 0.239005736 calories.
What is the formula to convert joules to calories?
Multiply the number of joules by 0.239005736. To reverse it, divide by 0.239005736 instead.
How do I convert calories back to joules?
Divide by 0.239005736, which is the same as multiplying by 4.184.
How many calories are in 10 joules?
10 J works out to 2.390057 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 joule defined?
Defined as 1 N·m, equivalently one watt-second. Named after James Prescott Joule.