Joules to calories

Multiply joules by 0.239006 to get calories.

1 J = 0.239006 calNIST SP 811

Convert

23.9006cal

100 J = 23.9006 cal

How to convert joules to calories

The calorie is the thermochemical calorie, exactly 4.184 joules. The joule is the SI unit of energy, one newton-metre (one watt for one second).

Worked example — 100 J: 100 × 0.239006 = 23.9006 cal.

Joules to calories table

Common conversions. The reverse table is on calories to joules.
Joules	Calories
1 J	0.239006 cal
5 J	1.195 cal
10 J	2.3901 cal
50 J	11.9503 cal
100 J	23.9006 cal
500 J	119.5029 cal
1,000 J	239.0057 cal
4,184 J	1,000 cal
10,000 J	2,390.0574 cal

Reverse and related

calories → joulesreverse conversion kWh → J1 kWh = 3,600,000 J kJ → cal1 kJ = 239.0057 cal BTU → J1 BTU = 1,055.0559 J kJ → J1 kJ = 1,000 J kcal → kJ1 kcal = 4.184 kJ kJ → kcal1 kJ = 0.239006 kcal

About joules and calories

Joule (J)

1 J = 0.239006 cal

Definition. The SI unit of energy, one newton-metre (one watt for one second)

History and origin

The joule is the SI unit of energy, named after James Prescott Joule, who showed in the 1840s that heat and mechanical work are equivalent. It is the work done by one newton acting over one metre.

Current use

Joules are the standard energy unit in physics and appear on appliance and equipment ratings.

Source: NIST SP 811, Appendix B; ISO 80000-5 (energy)

Calorie (cal)

1 cal = 4.184 J

Definition. The thermochemical calorie, exactly 4.184 joules

History and origin

The calorie was defined in the nineteenth century as the heat needed to raise one gram of water by one degree Celsius; the thermochemical calorie is now fixed at exactly 4.184 joules.

Current use

Calories are used in chemistry and to describe small amounts of energy; food labels use the larger kilocalorie.

Source: NIST SP 811, Appendix B; ISO 80000-5 (energy)

Where people use this

Joules: physics, appliance ratings. Calories: chemistry, small energy amounts. 4.184 J is exactly 1 calorie.

How we know this is right

The factor is fixed by the standards that define the units, not chosen — so it is exact, not a measurement:

1 cal = 4.184 J, so 1 J = 1 ÷ 4.184 = 0.239006 cal.

Every value is carried to full double precision; the display is rounded.

Both units are defined in NIST SP 811, Appendix B; ISO 80000-5 (energy).

Questions people ask

How many calories is 4.184 J?

4.184 joules is exactly 1 calorie.

How many calories in a joule?

One joule is about 0.239 calories.

How many joules is 100 calories?

100 calories is 418.4 joules.

All joule conversions

Calories to joules1 cal = 4.184 J Kilowatt-hours to joules1 kWh = 3,600,000 J British thermal units to joules1 BTU = 1,055.0559 J Kilojoules to joules1 kJ = 1,000 J