If you want to change kilojoules to Calories (kJ to Cal), or calories to kilojoules, use these handy converters. Then, read on to find out why food labels list kilojoules and energy rather than calories.
Kilojoules to Calories, kJ to Cal
In theory, it is simple: kilojoules and calories are different unit measures of the same thing. However, even professionals get confused when trying to use one or the other or both at the same time.
So many questions
Why do nutrition labels on food packages measure energy in kilojoules (kJ) instead of Calories (Cal)? Are they really the same thing? Why does it seem that there are thousands of kJ in foods but only hundreds of calories? Some people say kilocalories (kcal), whilst others say calories. Yet others insist on capitalising the “C” in in the word Calorie. How is is possible that some unit converters give wildly different results when changing kilojoules to calories compared to others? Why do we call ourselves Calorie Counter Australia instead of Kilojoule Counter Australia? So many questions, let’s get some answers!
Different units, same thing!
To be clear, for our purposes, both calories and kilojoules refer to the same thing: food energy.
Energy is the ability to do work.
Work is movement.
Therefore, both kilojoules and calories are words used to describe the amount of “get-up-and-go” in food! Read our home page to get a more detailed explanation of what, exactly, a calorie is.
Why Kilojoules on food packaging?
In Australia, government regulations and standards decree that food energy must be described as “kilojoules” or “kJ” in abbreviation. However, it has not always been this way. From 1812 to the 1970’s, food energy was officially denoted “calories” or “Cal” in abbreviation.
The shift from calories to kilojoules was just another one of the things that changed when we adopted the SI metric measurement system. Parliament passed the Australian Metric Conversion Act in 1970, and government agencies therefore followed through shortly thereafter.
That is why food packages list kJ instead of Cal today.
Why do we still use calories?
We still use calories instead of kilojoules for two main reasons:
Reason 1 – for most of our nation’s history, calories is the word most people used (and still use). Even if you were born after 1974 when the big changes happened, it is likely that kJ have not replaced calories in your mind. A difference which makes no difference is not a difference! We’re just used to calories!
Reason 2 – cultural transmission. Australia and New Zealand are arguably the only significant English-speaking countries to have officially opted for kilojoules over calories. That’s 30 million people supposedly saying “kilojoule”, versus 400 million saying “calorie”. As a result of almost every book, movie, TV show, podcast, webcast, song and article using “calories” rather than “kilojoules”, we do the same.
Fun fact: this music video is the massive Chinese hit song “Kaluli”. Kaluli is performed by a group of young ladies who sing about their determination to avoid calories (“kaluli”). Tellingly, the Chinese word for food energy, derived from English, is “kaluli” rather than “kilojuli”.
From this example of pop culture and many others, we can see that “calories” have seeped deeply into the world’s culture, whereas “kilojoules” have not.
Even the Scientists use calories
Furthermore, even the international scientific community has stubbornly refused to give up the calorie. Despite the global adoption of the SI unit system for science research, it seems that the current method in chemistry is to use kilocalories rather than kilojoules.
Food energy is measured by using a device called a bomb calorimeter. There is an entire specialisation in science known as calorimetry. The World Health Organisation talks about Daily per Capita calorie supply, rather than Daily per Capita kilojoule supply.
Now you know why we call ourselves Calorie Counter Australia, rather than Kilojoule Counter Australia!
When is a calorie a kilocalorie?
Just as there are one thousand joules (J) in a kilojoule (kJ), there are one thousand calories (cal) in a kilocalorie (kcal). In other words, both the calories system of measurement and the joules system use decimals.
Here comes the the tricky part: the generally accepted convention is to call kilocalories “Calories”, with an uppercase “C”, whilst calories (one thousandth of a kilocalorie) keep their lowercase “c”. Since “Calories” sounds the same as “calories”, the two meanings often get mixed up and people do not use a capital “C”, even when they mean kilocalories rather than calories. The abbreviation for Calories/kilocalories is “kcal” or “Cal” whereas the abbreviation for calories is “cal”.
This is why some unit conversion tools seem to offer wildly different results, depending on whether or not the users are expecting to see kilocalories or calories. Typing 1,200 calories into one of those converters gives you the result 5 kilojoules, which is about one third of a gram of Weet-Bix.
Are you confused yet?
To make matters worse, when most people talk about calories in food, they really mean kilocalories! That is, Calories rather than calories, kcal or Cal rather than cal. You’re on safe ground to assume that whenever the word “calorie” or the abbreviation “cal” is used in connection with food, the true meaning is kilocalories (kcal/Cal).
How to convert kilojoules to Calories kJ to Cal?
We convert kj to Cal and vice-versa by multiplying or dividing by the fixed conversion rate. One calorie (cal) is equal to 4.184 joules (J). This means that one Calorie/kilocalorie (Cal/kcal) is equal to 4.184 kilojoules (kJ).
The practical formula is:
E (Cal) = E (kJ) x 0.239
If you eat an extra banana every day for all of the time you are on a calorie-controlled diet, you will exceed your plan.
Skip the guesswork, use our calorie converter and get it right!
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