A calorimeter reports 500 J. How many calories is that?

About 119.5 cal (119.50286807 cal). Divide 500 by 4.184.

My data is in kJ. How many calories and kilocalories is 1 kJ?

About 239 cal, or 0.239 kcal. 1 kJ is 1,000 J, and 1,000 ÷ 4.184 gives 239.0057 cal.

My result differs from another table by about 0.07%. Why?

The other table may use the IT calorie of 4.1868 J. Dividing by 4.1868 instead of 4.184 gives a result about 0.07% smaller.

Is a food Calorie the same as the calorie here?

No. A food Calorie, written with a capital C, is 1 kcal, or 1,000 cal. With the thermochemical calorie used here, that is 4,184 J.

Joules (J) to Calories (cal) Converter

Enter a value to instantly convert between energy units.

From

Precision4 dp

1 Joule = 0.239 Calorie (thermochemical)

Key Formulas

Kilocalorie → Kilojoule

kJ = kcal × 4.184

Kilojoule → Kilocalorie

kcal = kJ × 0.239006

Kilowatt-Hour → Joule

J = kWh × 3600000

Joule → Kilowatt-Hour

kWh = J × 2.77778e-7

Formula

cal = J ÷ 4.184

If your heat data is in joules and a reference table uses calories, divide joules by 4.184 to get calories. This page uses the thermochemical calorie, which is 4.184 J by definition. The IT calorie is 4.1868 J, so check which calorie your source uses. The food Calorie on nutrition labels is the kilocalorie, or 1,000 cal. For the reverse, see calories to joules. For food energy, see kcal to kJ.

Source: NIST SP 811, Appendix B

Reviewed by the Convert Calc editorial team · Last reviewed: 2026-10-22 · see our methodology

Frequently Asked Questions

Real-World Examples

Example: 100 J of heat released by a reaction.

100 J = 23.900573613766728 cal

Example: 1 kJ of heat recorded by a calorimeter.

1000 J = 239.0057361376673 cal

Example: 4,184 J of heat, which is 1 kcal.

4184 J = 1000 cal

Example: 10 kJ of heat taken up by a water bath.

10000 J = 2390.057361376673 cal

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