How do I convert joules to calories?

Divide the energy in joules by 4.184. This converter uses the thermochemical calorie, defined as exactly 1 cal = 4.184 J. For example, 4.184 J = 1 cal.

How do I convert calories to joules?

Multiply the calories by 4.184. So 10 cal = 41.84 J. The converter works in both directions — type in either field and the other updates.

How many calories are in 1000 joules?

1000 ÷ 4.184 ≈ 239 cal. One kilojoule is therefore about 239 small calories, or about 0.239 food Calories (kcal).

What is the difference between a calorie and a Calorie (kcal)?

A small calorie (cal) is 4.184 J. The dietary Calorie on food labels is a kilocalorie — 1000 small calories, or 4184 J. This tool converts small calories; use the food-Calorie converter for nutrition labels.

Is this converter accurate?

Yes, for the thermochemical calorie (1 cal = 4.184 J exactly). Note that the 'large' food Calorie (kcal) is 1000 of these calories, and the international-table calorie (4.1868 J) differs slightly — this tool uses the thermochemical definition.

Why are there different definitions of the calorie?

The calorie was originally the heat needed to raise 1 g of water by 1 degree Celsius, which varies with temperature. The thermochemical calorie (4.184 J) and the international-table calorie (4.1868 J) are two standardised values; this tool uses the thermochemical one.

Is my data sent anywhere?

No. The converter is privacy-first — all processing happens locally in your browser and nothing you type leaves your device.

Joules to Calories Converter

The joule (J) is the SI unit of energy, while the calorie (cal) is an older unit still common in chemistry, physics and nutrition. This converter changes joules into calories and back again so you can move between datasheets, textbooks and lab results that use different units.

How it works

It uses the thermochemical calorie, defined as exactly 1 cal = 4.184 J:

Joules to calories: divide the joules by 4.184.
Calories to joules: multiply the calories by 4.184.

Type a value in either field and the other updates in real time. Note this is the small calorie — the dietary “Calorie” (kcal) on food labels is 1000 of these, so use the food-Calorie converter for nutrition figures.

Joules (J)	Calories (cal)
1	0.239
4.184	1
100	23.9
1000	239

Example

To convert 500 J, divide by 4.184: 500 ÷ 4.184 ≈ 119.5 cal. Going the other way, 100 cal equals 100 × 4.184 = 418.4 J.

All calculations run entirely in your browser with no data sent to any server.