What is the difference between kJ and kcal?

Both kJ (kilojoules) and kcal (kilocalories) are units of energy used in nutrition. 1 kcal equals 4.184 kJ. Some countries (such as Australia and most of Europe) label food energy primarily in kJ, while others (such as the US and UK) use kcal. The term 'calorie' on food labels almost always refers to kilocalories (kcal), not small calories (cal).

Is 100 kJ the same as 100 kcal?

No. 100 kJ equals approximately 23.9 kcal (100 divided by 4.184). Kilojoules are a smaller unit than kilocalories. To get kcal from kJ, always divide by 4.184.

How do I convert kcal back to kJ?

To convert kilocalories back to kilojoules, multiply by 4.184: kJ = kcal times 4.184. For example, 500 kcal equals 500 times 4.184 equals 2,092 kJ. This reverse conversion is shown automatically in the results section of this converter.

Kilojoules to Calories Converter (kJ to kcal)

Q: What is the formula to convert kilojoules to calories?

The formula is: kcal = kJ divided by 4.184. This uses the thermochemical calorie definition, where 1 kilocalorie (kcal) equals exactly 4.184 kilojoules (kJ). This is the standard conversion used in nutrition labelling and food science worldwide.

Q: How many kJ is 2000 kcal?

2,000 kcal equals 8,368 kJ (2,000 multiplied by 4.184). The average recommended daily energy intake for adults is approximately 2,000 kcal or 8,400 kJ, though this varies by age, sex, and activity level.

Energy in Kilojoules (kJ)

Decimal Precision

Conversion Result

Kilocalories (kcal)

Using formula: kcal = kJ ÷ 4.184

Calculation Details

Exact value: --
Rounded value: --
Reverse conversion: --
Formula applied: --

Quick Reference: kJ to kcal

Conversion formula: kcal = kJ ÷ 4.184
Reverse formula: kJ = kcal × 4.184
Conversion constant: 1 kcal = 4.184 kJ (thermochemical calorie definition)
Common values: 100 kJ = 23.90 kcal | 500 kJ = 119.48 kcal | 1000 kJ = 238.95 kcal | 8368 kJ = 2000 kcal
Daily energy reference: ~8,400 kJ = ~2,000 kcal (average adult daily intake guideline)
Last updated: March 2026

What Are Kilojoules and Calories?

Kilojoules (kJ) are the SI (International System of Units) unit of energy. In nutrition, kilojoules measure the energy content of food and drinks. Countries that follow SI conventions — including Australia, New Zealand, and EU member states — require food energy to be labelled in kilojoules.

Kilocalories (kcal), commonly called "Calories" (with a capital C) on food labels, measure the same thing: the energy released when your body metabolises food. One kilocalorie is the amount of energy needed to raise one kilogram of water by one degree Celsius. Countries such as the United States and much of South Asia primarily use kilocalories on food labels.

The two units are related by a fixed constant: 1 kcal = 4.184 kJ. This is the thermochemical calorie definition, the most widely used standard in nutrition and food science.

How to Use This Converter

Enter kilojoules: Type the energy value in kJ. Any non-negative value up to 10,000,000 kJ is accepted.
Choose decimal precision: Select 0, 1, 2 (default), or 3 decimal places for the kcal result.
Click Convert: The result shows immediately — primary kcal value, exact unrounded figure, and the reverse kJ conversion.

kJ to kcal Formula and Conversion Constant

The exact formula used in this converter is:

kcal = kJ ÷ 4.184

Where 4.184 is the thermochemical calorie conversion factor: 1 kcal = 4.184 kJ exactly.

The reverse conversion (kcal back to kJ) uses:

kJ = kcal × 4.184

Worked Example 1

Input: 200 kJ
kcal = 200 ÷ 4.184 = 47.798279... kcal (exact)
Rounded to 2 d.p.: 47.80 kcal
Reverse check: 47.80 × 4.184 = 199.99 kJ

Worked Example 2

Input: 8,368 kJ (approximate daily recommended intake)
kcal = 8,368 ÷ 4.184 = 1,999.04... kcal (exact)
Rounded to 0 d.p.: 1,999 kcal
Note: The standard 2,000 kcal guideline equals exactly 8,368 kJ

Common kJ to kcal Reference Values

Kilojoules (kJ)	Kilocalories (kcal)
100 kJ	23.90 kcal
250 kJ	59.74 kcal
500 kJ	119.48 kcal
1,000 kJ	238.95 kcal
2,000 kJ	477.91 kcal
4,184 kJ	1,000.00 kcal
8,368 kJ	1,999.04 kcal
10,000 kJ	2,389.49 kcal

Frequently Asked Questions

The formula is: kcal = kJ ÷ 4.184. This uses the thermochemical calorie definition, where 1 kilocalorie (kcal) equals exactly 4.184 kilojoules (kJ). This is the standard conversion used in nutrition labelling and food science worldwide.

Both kJ (kilojoules) and kcal (kilocalories) are units of energy used in nutrition. 1 kcal = 4.184 kJ. Some countries label food energy primarily in kJ, while others use kcal. The word "calorie" on food labels almost always means kilocalorie (kcal), not small calories (cal).

No. 100 kJ equals approximately 23.9 kcal (100 ÷ 4.184). Kilojoules are a smaller unit than kilocalories. To get kcal from kJ, always divide by 4.184.

2,000 kcal equals 8,368 kJ (2,000 × 4.184). The average recommended daily energy intake for adults is approximately 2,000 kcal or 8,400 kJ, though this varies by age, sex, and activity level.

This converter uses the thermochemical calorie, where 1 kcal = 4.184 kJ exactly. This is the most widely used definition in nutrition contexts. Other calorie definitions (such as the International Table calorie at 4.1868 kJ) differ slightly but are rarely used in everyday nutrition labelling.

To convert kilocalories back to kilojoules, multiply by 4.184: kJ = kcal × 4.184. For example, 500 kcal equals 500 × 4.184 = 2,092 kJ. This reverse conversion is shown automatically in the results section of this converter.

The joule is the SI (International System of Units) unit of energy, which is why countries following SI conventions — including Australia, New Zealand, and EU member states — require kJ on food labels. The kilocalorie remains widely understood colloquially, so many labels show both kJ and kcal side by side.

A small calorie (cal) is the energy needed to raise 1 gram of water by 1 degree Celsius. A kilocalorie (kcal) is 1,000 small calories. In everyday nutrition and on food packaging, the word "calorie" nearly always means kilocalorie. So when a food label says 200 calories, it means 200 kcal or 836.8 kJ.

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This tool belongs to Health Calculators. Browse similar tools for related calculations.

This converter is for informational and educational purposes. Nutritional energy values on food labels may use slightly different rounding. Always refer to official food labels for precise dietary information.

Kilojoules to Calories Converter