Kilojoules to kilocalories:
divide by 4.184

How many kcal are in a kilojoule?

One kilojoule is 0.2390057361 kilocalories, or about 0.239 kcal. Put the other way round, one kilocalorie equals 4.184 kilojoules. The kilocalorie here is the food Calorie, the unit most people simply call a calorie when counting what they eat.

Both units measure energy. The kilojoule is the metric (SI) unit and the kilocalorie is the older unit still widely used on nutrition labels. Many food packets list both, and some countries show kJ first, which is why a quick conversion is handy.

The kJ to kcal formula

1. 1Read the energy value in kJ from the label.
2. 2Divide by 4.184.
3. 3Round to a whole number, since labels are only approximate anyway.
4. 4Check the answer: it should be a little under a quarter of the kJ figure.

Chart: kJ to kcal

Values are rounded from the exact factor. For any other figure, divide by 4.184 or use the converter.

Real uses: food labels and daily totals

Labels in Australia, New Zealand and across Europe show kJ alongside kcal, while labels in the United States use Calories only. If you track intake in kcal but a packet lists only kJ, divide by 4.184. A daily total of 8,700 kJ, for example, is 8,700 ÷ 4.184 = 2,079.35 kcal.

Going the other way, a 500 kcal meal is 500 × 4.184 = 2,092 kJ, and a 250 kcal bar is 1,046 kJ. These figures are estimates for comparing foods, not medical or dietary advice, so speak to a qualified professional about your own needs.

More examples: adding up a meal

Convert a total, not each item, to avoid piling up rounding errors. A meal of three items with 350 kJ, 600 kJ and 1,200 kJ comes to 2,150 kJ, and 2,150 ÷ 4.184 = 513.9 kcal. Converting each item to a whole number first would give 84 + 143 + 287 = 514, which is close but not identical.

A single item works too: 350 kJ is 83.65 kcal, so a snack labelled 350 kJ is roughly 84 kcal. These numbers are labelling estimates and can vary from product to product, so treat them as a guide.

Remember too that a kilocalorie is written with a capital C as Calorie on many labels. A food Calorie and a kilocalorie are the same thing, while a small calorie is a thousand times smaller, so a label never means the small one.

Common mistakes when converting kJ to kcal

• Multiplying by 4.184 when you should divide. kcal is the larger unit, so the kcal number is smaller than the kJ number.
• Mixing up kcal and cal. A small calorie (cal) is one thousandth of a kilocalorie, and food labels use kcal.
• Rounding 4.184 to 4.2 or 4 too early, which skews totals over several foods.
• Adding kJ and kcal values from different packets without converting to one unit first.