How to convert kilojoules to calories
There are 4.184kJ in 1 food calorie (kcal). To roughly convert kilojoules to calories, divide your kJ figure by 4.2 or multiply it by 0.24. Note that when we talk about calories, we are actually describing food calories (kilocalories).
Calories (kcal) = kJ ÷ 4.184
As an example, let's say you're pouring yourself a glass of orange juice which supplies 400kJ of energy, and you want to convert it into calories. To do so, you divide it by 4.184, which gives you a figure of around 96 calories.
How to convert calories to kilojoules
As there are 4.184kJ in 1 food calorie (kcal), you can roughly convert calories to kilojoules by multiplying your calorie figure by 4.2.
kJ = calories (kcal) × 4.184
What are kilojoules?
With the introduction of the metric system in many countries, the kilojoule (kJ) replaced the food calorie (kcal) in measurements of food energy. This has created a need for converting between kilojoules and calories.
- A kilojoule (kJ) is a unit of energy in the International System of Units (SI)
- A food calorie (kcal), also known as a kilocalorie, is the amount of energy needed to raise the temperature of 1 kilogram of water by 1°C
- Both units measure the same thing — energy from food — just in different scales
Kilojoules to calories chart
| kJ | Calories (kcal) |
|---|---|
| 1 kJ | 0.239 calorie |
| 2 kJ | 0.478 calorie |
| 3 kJ | 0.717 calorie |
| 4 kJ | 0.956 calorie |
| 5 kJ | 1.195 calories |
| 10 kJ | 2.39 calories |
| 20 kJ | 4.78 calories |
| 30 kJ | 7.17 calories |
| 40 kJ | 9.56 calories |
| 50 kJ | 11.95 calories |
| 60 kJ | 14.34 calories |
| 70 kJ | 16.73 calories |
| 80 kJ | 19.12 calories |
| 90 kJ | 21.511 calories |
| 100 kJ | 23.901 calories |
Note that conversions in the above chart are rounded to a maximum of 3 decimal places.
How many calories are in 500kJ?
500kJ is equal to 119.5 calories. You can calculate this by dividing 500 by 4.184, as there are 4.184kJ in 1 food calorie.
Common food energy values
| Food Item | Energy (kJ) | Energy (kcal) |
|---|---|---|
| Apple (medium) | 400 kJ | 96 kcal |
| Banana (medium) | 360 kJ | 86 kcal |
| Orange juice (1 glass) | 400 kJ | 96 kcal |
| Chicken breast (grilled) | 690 kJ | 165 kcal |
| Rice (1 cup, cooked) | 1,000 kJ | 239 kcal |
| Egg (large) | 310 kJ | 74 kcal |
| Bread (1 slice) | 440 kJ | 105 kcal |
Which countries use kilojoules?
Countries that use the metric system typically display energy in kilojoules on food labels, including:
- Australia — kJ is the primary unit on nutrition labels
- New Zealand — kJ is required on food packaging
- South Africa — kJ is used alongside kcal
Countries that predominantly use food calories (kcal):
- United States — kcal shown as "Calories" on nutrition labels
- European Union — both kJ and kcal are displayed
- United Kingdom — both kJ and kcal are displayed
Quick conversion tips
- Rough estimate: Divide kJ by 4 to get approximate calories
- Quick reverse: Multiply calories by 4 to get approximate kJ
- Precise conversion: Use 4.184 as the conversion factor
- Remember: 1 food calorie = 1,000 small calories = 4.184 kJ