Kilojoules to kilocalories
Convert kilojoules to kilocalories. Divide by 4.184, with tables for EU and Australian food labels and daily intake.
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The formula
kcal = kJ ÷ 4.184Equivalently, multiply by 0.2390057. The 4.184 is exact by convention — the thermochemical calorie was defined as that many joules rather than measured.
To go the other way, multiply by 4.184. See kcal to kJ.
Why a label is in kilojoules
EU and Australian regulations require energy to be declared in kilojoules, with kilocalories optional alongside. Anyone used to counting in calories therefore has to divide by roughly four to read a European or Australian packet.
The kilojoule is the SI-consistent unit and the kilocalorie is the historical one. Neither is more correct; the difference is which regulator wrote the rule.
Quick reference
| kJ | kcal |
|---|---|
| 100 kJ | 24 kcal |
| 250 kJ | 60 kcal |
| 500 kJ | 120 kcal |
| 1000 kJ | 239 kcal |
| 2000 kJ | 478 kcal |
| 4184 kJ | 1000 kcal |
| 8368 kJ | 2000 kcal |
| 10,000 kJ | 2390 kcal |
1000 kJ is 239 kcal and 8400 kJ is about 2000 kcal are the two anchors worth keeping.
Daily intake on a kilojoule label
Australian labels use 8700 kJ as the reference daily intake, where European and British labels use 2000 kcal:
| Reference | kJ | kcal |
|---|---|---|
| Australian daily intake | 8700 | 2079 |
| EU reference intake | 8368 | 2000 |
| Men, typical guidance | 10,460 | 2500 |
| Women, typical guidance | 8368 | 2000 |
The Australian figure is 4% higher than the European one, which is why the same product shows slightly different ”% of daily intake” percentages in the two markets.
Per 100 g against per serving
The commonest error reading a label is not the unit but the basis. European labels must give energy per 100 g; a per-serving column is optional and the serving may be a fraction of the pack:
| Per 100 g | Per 40 g serving | |
|---|---|---|
| Breakfast cereal | 1600 kJ / 382 kcal | 640 kJ / 153 kcal |
| Crisps | 2200 kJ / 526 kcal | 880 kJ / 210 kcal |
Converting the wrong column gives an answer that is correct arithmetic about the wrong quantity.
Estimating in your head
Divide by 4 and take off 5%. 2000 kJ ÷ 4 is 500, minus 25 is 475 kcal — the true answer is 478. Dividing by 4 alone runs 4.6% high, which is close enough for a shelf.
For a rougher rule still: kilojoules to calories is roughly a quarter, and the error is always in the same direction.