UrbiTools

Joules to Calories Converter

Convert joules to calories and back — with the small-calorie vs food-calorie distinction that trips everyone up.

Convert joules ⇄ calories

239.0057 cal
1000 J = 239.0057 cal

Formula: 1000 J (J ÷ 4.184) = 239.0057 cal

How the joules to calories conversion works

The conversion is exact by definition: calories = joules ÷ 4.184. One (small) calorie is the energy needed to raise one gram of water by one degree Celsius, defined as exactly 4.184 joules. Going the other way, joules = calories × 4.184.

Small cal vs food Calorie: food labels use kilocalories (kcal), written with a capital C as “Calories”. One food Calorie = 1,000 small calories = 4,184 joules. So 1,000 J is 239 small calories but only 0.239 food Calories. If you are converting a food label, divide the result here by 1,000 — or use our kcal to kJ converter.

Worked example: 1,000 J is 1,000 ÷ 4.184 = 239.01 cal (0.239 kcal). And 500 cal is 500 × 4.184 = 2,092 J. For larger energy amounts, see kWh to joules.

Handy benchmarks: 100 J = 23.90 cal, 1,000 J = 239.01 cal, 4,184 J = 1,000 cal (1 kcal) and 10,000 J = 2,390.06 cal.

joules to calories converter questions

How many calories are in 1 joule?
0.239 calories (small calories). 1 ÷ 4.184 = 0.2390 cal. In food Calories (kcal), 1 joule is just 0.000239 kcal.
How do I convert joules to calories?
Divide by 4.184: cal = J ÷ 4.184. So 1,000 J is 239.01 cal.
What is the difference between cal and kcal?
One kilocalorie (kcal, or food “Calorie”) equals 1,000 small calories. Food labels quote kcal; physics problems usually mean small cal. Multiply or divide by 1,000 to move between them.
How many joules are in 100 calories?
418.4 J — 100 small calories × 4.184. If you meant 100 food Calories, that is 100 kcal = 418,400 J.
How do I convert calories back to joules?
Multiply by 4.184: J = cal × 4.184. Switch the direction above to do it.

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Sources & official guidance

Exact conversion — 1 cal = 4.184 J by definition. Food labels use kcal (1 kcal = 1,000 cal). See our disclaimer.