Catherine Saxelby's Foodwatch | How to convert kilojoules to calories

How to convert kilojoules to calories

Just like yards became metres and pounds became grams, so calories have become kilojoules. Kilojoules are the metric equivalent of calories and have replaced calories in almost all countries. Yet they're very confusing, especially to my US visitors who have always only known calories (lucky for me, I grew up with calories then had to learn kilojoules!)

These are the units used to measure food energy - kilojoules (abbreviated to kJ) and Calories (Cals). Kilojoules are four times larger than calories eg a bowl of cereal supplies around 480 kilojoules or 117 Calories.

Conversion is 4.2 ... or just 4

1 calorie equals 4.186 kilojoules (4.2 or simply 4 is close enough for a quick conversion).
For example, a slice of bread supplies 290 kilojoules or (290 divided by 4) 70 Calories.

Kilojoules are difficult to grasp if you don't have a feel for the numbers. So here's a handy guide to make things more ‘friendly'.

Here's how food compares in kilojoules and calories:

Tip

Round the kilojoules to the nearest 0 or 5. So 288kJ rounds up to 290kJ while 292 rounds down to 290kJ. Five kilojoules translates to 1 calorie which is hardly anything and makes your useage of kilojoules easier as there's fewer digits to remember. We round off all the kilojoule counts on our recipes for ease of use - see here.

Rule of thumb

To obtain calories, divide kilojoules by 4 for a quick conversion.

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Read why I think the term "energy" is one of the most misunderstood in nutrition. Click here.