Calories to JoulesFree online conversion calculator — instant results, no sign-up
Convert calories to joules and back.
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About the Calories to Joules
The Calories to Joules calculator converts energy measured in calories into joules using 1 calorie = 4.184 joules. It also shows the reverse conversion rate from joules to calories. Here, “calorie” means the small thermochemical calorie, not the dietary Calorie used on food labels.
- Value in calories (calories)
- The energy amount to convert, measured in small thermochemical calories (cal), with a default value of 1.
Formula and method
E_J = E_cal × 4.184; reverse conversion: E_cal = E_J ÷ 4.184.
- E_JEnergy measured in joules (J).
- E_calEnergy measured in thermochemical calories (cal).
Multiply the calorie input by 4.184 joules per calorie. For the default input of 1 calorie, the result is 4.184 joules. The reverse unit rate is calculated by dividing 1 joule by 4.184, giving approximately 0.239006 calories.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Value in calories1 calories
Results
- joules4.184
- 1 calories =4.184 joules
- 1 joules =0.239006 calories
How to use the Calories to Joules
- 1Check that your energy amount is in small calories (cal), rather than dietary Calories (kcal).
- 2Enter the amount in the Value in calories (calories) field, or leave the default value of 1.
- 3Read the joules result, calculated by multiplying the input by 4.184.
- 4Use the forward equivalence row to confirm that 1 calorie equals 4.184 joules.
- 5Use the reverse equivalence row to see that 1 joule equals approximately 0.239006 calories; for a reverse calculation, divide the joule amount by 4.184.
Reading your result
With the default input, “joules = 4.184” is the converted energy amount. The row “1 calories = = 4.184 joules” states the forward unit equivalence. The row “1 joules = = 0.239006 calories” states the reverse unit equivalence, rounded to six decimal places; it is not a conversion of the 4.184-joule result back to calories. The duplicated equals signs in these rows should be read as a single equals sign.
Limitations
The calculator assumes the thermochemical definition of a calorie, for which 1 cal equals exactly 4.184 J. Other calorie definitions can give slightly different results. A dietary Calorie (Cal) is a kilocalorie, equal to 1,000 small calories, so food-label values must be converted to small calories before entry. Displayed results may be rounded, and conversion does not improve the precision of the original measurement.
Common questions
Can I enter Calories from a food label directly?+
Not as small calories. Food-label Calories are kilocalories, so multiply the label's Calorie amount by 1,000 before entering it in this calculator.
Why does the default input produce 4.184 joules?+
The default input is 1 calorie, and the thermochemical calorie is defined as exactly 4.184 joules. Multiplying 1 by 4.184 therefore gives 4.184 joules.
Is 0.239006 calories per joule exact?+
No. The exact reverse factor is 1 ÷ 4.184 calories per joule. The displayed value of 0.239006 is rounded to six decimal places.
How do I convert joules back to calories?+
Divide the energy in joules by 4.184. The reverse equivalence row shows the unit rate: 1 joule is approximately 0.239006 calories.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.