How to convert kilojoules to Calories

Written by Catherine Saxelby on Wednesday, 30 September 2009.
Tagged: Calories, dieting, diets, energy, fat loss, food labels, FSANZ, guides, kilojoules, nutrients, nutrition, technology

How to convert kilojoules to Calories
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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 Australia and many other metric 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). Like other food scientists, I use the capital C as shorthand for the longer correct term of kilocalories

Kilojoules LOOK four times larger than Calories simply because there are more digits 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'.


How diets compare in kilojoules and Calories              

kilojoules   kJ                                    
Calories  Cals                            
Intake or level                                         
10000 2400 Typical level of intake of most teenagers
  8700 2070 Average intake used to calculate %DI on food labels
  7500 1800 Typical weight loss level for a moderately-active man
  7000 1650 Typical weight loss level for a sedentary man
  6000 1500 Typical weight loss level for a moderately-active woman
  5000 1200 Typical weight loss level for a sedentary woman
  4000 1000

Supervised fast or meal replacement intake
- too low for normal living and activity


Here's how food compares in kilojoules and Calories:

Food Amount                   
Bread 1 slice 30 g 290 70
Egg 1 large 60 g 335 80
Canned salmon, drained 1 can 150 g 525 125
Tim Tam chocolate biscuits 2 38 g 840 200
Krispy Kreme doughnuts, original glazed 2 104 g 1680 400
Orange juice 1 glass 250ml 400 95


orange-juice-smll1 glass orange juice = 400 kJ or 95 Calories


Round the kilojoules to the nearest 0 or 5. So 288 kJ rounds up to 290 kJ, while 292 rounds down to 290 kJ. 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.

Rule of thumb

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

Catherine Saxelby About the author

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Catherine Saxelby has the answers! She is an accredited nutritionist, blogger and award-winning author. Her award-winning book My Nutritionary will help you cut through the jargon. Do you know your MCTs from your LCTs? How about sterols from stanols? What’s the difference between glucose and dextrose? Or probiotics and prebiotics? What additive is number 330? How safe is acesulfame K? If you find yourself confused by food labels, grab your copy of Catherine Saxelby’s comprehensive guide My Nutritionary NOW!