kJ to kcal: How to Read Calories on a Food Label

The short answer

To convert kilojoules (kJ) to kilocalories (kcal), divide by 4.184. So 1,000 kJ is about 239 kcal, and a 2,000 kcal daily intake is about 8,368 kJ. The "Calories" on a food label, written with a capital C, are kilocalories. Type any figure into the Energy Converter and switch between kJ and kcal to get the exact value.

kJ, kcal and Calories: what each one means

• Kilojoule (kJ): the metric (SI) unit of energy. Food labels in Australia and New Zealand must show energy in kilojoules.
• Kilocalorie (kcal): 1,000 small calories. This is the unit people usually mean when they talk about calories in food.
• Calorie with a capital C: another name for the kilocalorie, used on US labels and in everyday speech. "A 250-Calorie snack" means 250 kcal.
• calorie with a small c (cal): the small calorie, one thousandth of a kcal. You rarely see it on food.

The link between them is 1 kcal = 4.184 kJ. That is the value the Lazyblink converter uses.

Quick conversion table

Kilojoules	Kilocalories
100 kJ	23.9 kcal
418.4 kJ	100 kcal
500 kJ	119.5 kcal
1,000 kJ	239.0 kcal
2,000 kJ	478.0 kcal
8,700 kJ	2,079.3 kcal

And from kilocalories to kilojoules, multiply by 4.184:

Kilocalories	Kilojoules
100 kcal	418.4 kJ
250 kcal	1,046 kJ
500 kcal	2,092 kJ
2,000 kcal	8,368 kJ
2,500 kcal	10,460 kJ

How to convert with the Energy Converter

Open the Energy Converter.

Type the number from the label, for example 1000.

Set From to Kilojoule (kJ) and the target to Kilocalorie (kcal).

Read the result: 239.00573614 kcal. Round it to 239 kcal.

Use the swap button to go the other way.

The list below the result also shows the same energy in joules, small calories, watt-hours, kilowatt-hours and BTU. That is useful for other jobs, such as comparing a food's energy with an appliance's electricity use, but you can ignore it for food labels.

Why the two numbers on a label do not always match 4.184

If you check a European label with the converter, you may find the kJ and kcal figures are not exactly 4.184 apart. That is expected.

Under EU food labelling rules (Regulation 1169/2011, Annex XIV), the energy of a food is calculated from its nutrients using separate conversion factors for each unit:

Nutrient	kJ per gram	kcal per gram
Carbohydrate	17	4
Protein	17	4
Fat	37	9
Alcohol	29	7
Fibre	8	2

These factors are rounded, so the ratio between them is not always 4.184. Fat, for instance, is 37 kJ but 9 kcal, a ratio of about 4.11.

Worked example. A serving with 10 g fat, 30 g carbohydrate and 5 g protein:

• In kJ: (10 × 37) + (30 × 17) + (5 × 17) = 370 + 510 + 85 = 965 kJ
• In kcal: (10 × 9) + (30 × 4) + (5 × 4) = 90 + 120 + 20 = 230 kcal

If you convert 230 kcal with the 4.184 factor you get 962.3 kJ, not 965 kJ. The label is still correct; it was calculated from the nutrients, not converted from one unit to the other. Labels also round figures, which adds a few more units of difference.

Practical rule: when a label shows both units, use the one that matches your tracking app. Only convert when the label shows a single unit.

Reading labels from different countries

• Australia and New Zealand: energy must be shown in kilojoules. Some products also show Calories, but many show only kJ. Divide by 4.184, or use the converter, to compare with a calorie target.
• EU and UK: the nutrition declaration must show energy in both kJ and kcal.
• USA: labels show Calories, meaning kcal.
• India: FSSAI labelling guidance asks for energy in kcal.

Check whether the figure is per 100 g, per serving, or per pack. Converting units correctly but mixing up per 100 g and per serving is a far bigger error than any rounding.

Common mistakes

• Treating kJ as calories. A muesli bar with 800 kJ is about 191 kcal, not 800 Calories. Confusing the two inflates your count about four times.
• Multiplying instead of dividing. kJ to kcal is a division by 4.184. If your answer is bigger than the kJ figure, you went the wrong way.
• Using 4 or 4.2 as the factor. Dividing by 4 is a rough mental shortcut; it overstates kcal by about 4.6%. Fine for a quick check, not for tracking.
• Comparing per-serving with per-100 g. Always line up the same basis before comparing two products.

Using the numbers

Once you have a kcal figure, you can compare it with an estimate of your daily needs from the Calorie Calculator, which shows results in calories (kcal). If your tracker or dietitian works in kilojoules, convert the calculator's figure back with the Energy Converter.

For kitchen measurements, such as converting cups or grams in a recipe, see Kitchen and Cooking Unit Conversions.