By Tim King · Updated 1 October 2026

Joules to Calories and Calories to Joules

Divide Joules by 4.184 for Thermochemical Calories, Food kcal Explained

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joules to calories formula

cal = J ÷ 4.184

1 joule = 0.2390057361 calories, so multiply joules by 0.2390057361. Going the other way, 1 calorie = 4.184 joules.

joules to calories table

joules (J)	calories (cal)
1	0.239006
4.184	1
10	2.39006
50	11.9503
100	23.9006
418.4	100
500	119.503
1,000	239.006
2,000	478.011
4,184	1,000
5,000	1,195.03
10,000	2,390.06
50,000	11,950.3
100,000	23,900.6
1,000,000	239,006

How many calories in joules?

1 J = 0.239006 cal. There are 0.239006 calories in 1 joules.

100 J = 23.9006 cal. There are 23.9006 calories in 100 joules.

1,000 J = 239.006 cal. There are 239.006 calories in 1,000 joules.

4,184 J = 1,000 cal. There are 1,000 calories in 4,184 joules.

10,000 J = 2,390.06 cal. There are 2,390.06 calories in 10,000 joules.

calories to joules formula

J = cal × 4.184

1 calorie = 4.184 joules, so multiply calories by 4.184, or divide by 0.2390057361.

calories to joules table

calories (cal)	joules (J)
1	4.184
10	41.84
50	209.2
100	418.4
239	999.976
500	2,092
1,000	4,184
2,000	8,368
5,000	20,920
10,000	41,840
100,000	418,400
1,000,000	4,184,000

How many joules in calories?

1 cal = 4.184 J. There are 4.184 joules in 1 calories.

10 cal = 41.84 J. There are 41.84 joules in 10 calories.

100 cal = 418.4 J. There are 418.4 joules in 100 calories.

1,000 cal = 4,184 J. There are 4,184 joules in 1,000 calories.

2,000 cal = 8,368 J. There are 8,368 joules in 2,000 calories.

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How the Joules To Calories works

This joules to calories converter divides by 4.184 as you type, using the thermochemical calorie used in chemistry and physics. The result is in small calories; food labels use kilocalories, a thousand times larger, so the table gives both. Press the swap button to turn calories into joules.

The joule is the SI unit of energy, used for everything from the heat in a chemical reaction to the energy in a battery. The calorie is an older unit, defined originally as the heat needed to warm one gram of water by one degree Celsius. It survives in chemistry textbooks, in some engineering tables and, a thousand times larger, on every food label in the US and UK.

Joules to calories: which calorie?

Thermochemical calorie (cal): exactly 4.184 J. Chemistry and this converter use it.
International Steam Table calorie (cal_IT): exactly 4.1868 J, used in some engineering and steam tables. It is 0.07% larger.
Food Calorie (kcal or Cal): 1,000 small calories, or 4,184 J. Nutrition labels mean this when they say "calories", often with a capital C.

The formula

cal = J ÷ 4.184, and J = cal × 4.184. For food energy, kcal = J ÷ 4,184, or equivalently kcal = kJ ÷ 4.184.

Worked examples

The first example comes from the chemistry lab. Warming 250 g of water by 20 °C takes 250 × 20 × 4.184 = 20,920 J, and 20,920 ÷ 4.184 = 5,000 cal, which is 5 kcal.

The second example goes the other way. A 250 kcal snack bar holds 250,000 small calories, and 250,000 × 4.184 = 1,046,000 J, or about 1.05 MJ.

A third example: lifting a 1 kg bag 1 metre takes about 9.8 J, which is 2.3 cal, a tiny amount compared with the energy in food.

How many calories in common amounts of joules

There are 0.239 calories in a joule and 4.184 joules in a calorie. The table converts common joule amounts into small calories and into the kilocalories found on food labels.

Common energy amounts in joules with calories and kilocalories

Joules	Calories (cal)	Kilocalories (kcal)
1	0.239	0.000239
4.184	1	0.001
10	2.39	0.00239
100	23.9	0.0239
418.4	100	0.1
1,000	239	0.239
2,000	478	0.478
4,184	1,000	1
5,000	1,195	1.195
10,000	2,390	2.39
20,000	4,780	4.78
41,840	10,000	10
50,000	11,950	11.95
100,000	23,900	23.9
418,400	100,000	100
1,000,000	239,006	239
2,092,000	500,000	500
3,600,000	860,421	860.4
4,184,000	1,000,000	1,000
8,368,000	2,000,000	2,000
10,460,000	2,500,000	2,500

How to read the result

J equals gives the energy in small calories, for example 1,000 J equals 239 cal.
Conversion shows the factor, 1 J = 0.239 cal. After a swap it reads 1 cal = 4.184 J.
Inverse gives the factor for the opposite direction.

For a food figure, divide the result by 1,000 to get kilocalories.

Tips and pitfalls

Food calories are kilocalories. A 2,000-calorie diet is 2,000 kcal, or 8.4 million joules. Mixing them up gives answers a thousand times off.
Food labels in kJ. Australian, New Zealand and EU labels lead with kilojoules; use the kJ to calories converter for those.
Engineering tables may use 4.1868. Check which calorie a steam table or older HVAC reference uses; the difference is under 0.1%.
Electrical energy. For energy from appliances and bills, convert with joules to kWh. One kWh is 3.6 MJ, about 860 kcal.

FAQ

How many calories are in a joule?

One joule is 0.239 small calories, or 0.000239 food kilocalories. The calorie is the larger unit: one thermochemical calorie is exactly 4.184 joules, so you divide joules by 4.184 to get calories.

How many joules are in a calorie?

A thermochemical calorie is exactly 4.184 joules. A food Calorie, written kcal or Cal, is 1,000 times larger at 4,184 joules. The International Table calorie used in some engineering work is 4.1868 joules.

Is a food calorie the same as a calorie?

No. The calorie on a food label is a kilocalorie, 1,000 small calories or 4,184 joules. Scientists use the small calorie, so a 100-calorie biscuit holds 100,000 small calories, or 418,400 joules.

How many joules does a person use in a day?

An adult using 2,000 to 2,500 kcal a day uses about 8.4 to 10.5 million joules, or 8,400 to 10,500 kJ. That averages out to roughly 100 to 120 watts, about the same as an old incandescent light bulb.

Why is the calorie defined as 4.184 joules?

It was originally the heat to warm a gram of water by 1 °C, but that varies with the starting temperature. In the twentieth century chemists fixed it at exactly 4.184 joules so the unit would never drift.