Convert kilojoules to kilocalories
One kilojoule (kJ) equals 0.239006 kilocalories (kcal), so divide kilojoules by 4.184 to get kilocalories.
How do you convert kilojoules to kilocalories?
Why does 4.184 not match the kcal printed on the label?
Because a European label does not derive its kcal figure from its kJ figure. Both are calculated separately from the nutrient content using the factor table in Annex XIV of Regulation (EU) No 1169/2011, where protein and carbohydrate count as 17 kJ or 4 kcal per gram and fat as 37 kJ or 9 kcal per gram. Those pairs imply 4.25 and 4.111 kJ per kcal, not the physical 4.184, so the two numbers on a packet are usually a percent or so out of step with each other. This page converts with the exact physical factor: 1 kcal is 4.184 kJ.
What that means when you check a packet
Convert a label's kilojoules with 4.184 and you will land about 1.6 percent above the printed kcal for a pure carbohydrate or protein food, and about 1.7 percent below it for a pure fat. Neither figure is an error. The printed pair comes from the legal factors and your conversion comes from the physics, and for anything short of a laboratory both are perfectly usable.
The factor is 4.184, not 1,000
Kilojoules and kilocalories are not a metric power of ten apart, which is the other classic mistake on this pair. One kilocalorie is 4.184 kJ, so 1,046 kJ is 250 kcal and a 3,000 kJ meal is 717.02 kcal. The clean factor of 1,000 belongs to kilocalories and small calories, which is a different conversion entirely.
A head estimate that actually works
Divide kilojoules by four and you overshoot the kilocalories by about 4.6 percent; divide by 4.2 and you are within four tenths of a percent. For a 1,500 kJ portion that is 375 kcal by the rough method, 357 kcal by the better one and 358.51 kcal exactly, which is close enough to read a shelf label without a calculator.
Which calorie the 4.184 comes from
It is the thermochemical calorie, defined as exactly 4.184 joules, so a kilocalorie is exactly 4,184 J. Older engineering sources sometimes use the international steam table calorie of 4.1868 J instead, a difference of about seven hundredths of a percent. That never matters on a cereal box, but it does show up when a food figure is compared against an older thermodynamic table.
The EU energy conversion factors behind a nutrition label
Conversion factors from Annex XIV of Regulation (EU) No 1169/2011. The final column is calculated, and it is the reason a label's kJ and kcal figures do not divide by exactly 4.184.
| Nutrient | kJ per gram | kcal per gram | Implied kJ per kcal |
|---|---|---|---|
| Carbohydrate (except polyols) | 17 | 4 | 4.25 |
| Polyols | 10 | 2.4 | 4.167 |
| Protein | 17 | 4 | 4.25 |
| Fat | 37 | 9 | 4.111 |
| Salatrims | 25 | 6 | 4.167 |
| Alcohol (ethanol) | 29 | 7 | 4.143 |
| Organic acid | 13 | 3 | 4.333 |
| Fibre | 8 | 2 | 4 |
| Erythritol | 0 | 0 | not applicable |
This table has a page of its own: The EU energy conversion factors behind a nutrition label adds the same annex with each factor's gap from the physical 4.184 worked out, names every source, and is free to embed or republish with credit.
Sources
Kilojoule to kilocalorie conversion table
| Kilojoules | Kilocalories | Kilocalories | Kilojoules |
|---|---|---|---|
| 1 kJ | 0.239006 kcal | 1 kcal | 4.184 kJ |
| 2 kJ | 0.478011 kcal | 2 kcal | 8.368 kJ |
| 3 kJ | 0.717017 kcal | 3 kcal | 12.552 kJ |
| 5 kJ | 1.195 kcal | 5 kcal | 20.92 kJ |
| 10 kJ | 2.3901 kcal | 10 kcal | 41.84 kJ |
| 20 kJ | 4.7801 kcal | 20 kcal | 83.68 kJ |
| 50 kJ | 11.9503 kcal | 50 kcal | 209.2 kJ |
| 100 kJ | 23.9006 kcal | 100 kcal | 418.4 kJ |
| 500 kJ | 119.5 kcal | 500 kcal | 2092 kJ |
| 1000 kJ | 239.01 kcal | 1000 kcal | 4184 kJ |
To convert kilojoules to kilocalories, divide the number of kilojoules by 4.184. One kilojoule equals 0.239006 kilocalories, and one kilocalorie equals 4.184 kilojoules, so the relationship is fixed and exact. As a worked example, 10 kJ comes to 2.3901 kcal. Enter your own figure in the converter above to get an instant answer, or use the swap button to flip the direction. This is a energy conversion, and like every tool on UnitGlide it runs locally in your browser with no account or upload required. The table further down shows a range of common kilojoule values already worked out in kilocalories, plus the reverse kilocalorie to kilojoule direction, which is handy for quick reference or double-checking a result by hand.
Kilojoule to kilocalorie in practice
Kilojoules to kilocalories is the conversion European food labels force on anyone who thinks in Calories, because the EU lists energy in kilojoules first.
Reading a European label
EU nutrition labels give energy in kilojoules and kilocalories side by side, but much of the world only counts kcal, so a snack listed as 837 kJ is the 200 kcal a dieter is watching. Fitness apps that import kJ from a barcode need the same step to show a familiar Calorie figure, and a 2,000 kcal daily target is 8,368 kJ the other way round.
Energy in, not power
The kilojoule here is an amount of energy in a food, not a rate, so it converts straight to kilocalories. It is a different quantity from the kilowatts on an appliance or the kilojoules-per-second that make up a watt, and keeping food energy separate from power ratings avoids mixing two unrelated conversions.
Portion sums
Because labels state energy per 100 grams as well as per portion, this conversion often runs twice: first to turn the per-100-gram kJ into kcal, then to scale it to the amount actually eaten. A cereal at 1,500 kJ per 100 g is 359 kcal per 100 g, so a 40 g bowl is about 144 kcal, the kind of chain a calorie-counter runs off an EU packet all day.
Frequently asked questions
How many kcal is 1000 kJ?
1,000 kJ is 239.01 kcal. Divide kilojoules by 4.184, or multiply by 0.239006, which is the same step.
How do I convert kJ to kcal in my head?
Divide by 4.2. That lands within about four tenths of a percent of the exact answer, which is far closer than the common shortcut of dividing by four.
Why does my converted kcal not match the number on the packet?
EU labels calculate kilojoules and kilocalories independently from the nutrient content using the factors in Annex XIV of Regulation 1169/2011, and those factors imply 4.25 kJ per kcal for protein and carbohydrate and 4.111 for fat. Converting with the physical 4.184 therefore gives a slightly different number, typically within a couple of percent.
How many kilocalories are in a kilojoule?
One kilojoule equals 0.239006 kilocalories. The ratio is constant, so you can multiply any number of kilojoules by 0.239006 to get kilocalories.
What is the formula to convert kilojoules to kilocalories?
Use kilocalories = kilojoules ÷ 4.184. UnitGlide applies this exact formula for every value, so results stay accurate across the whole range.
How do I convert kilocalories back to kilojoules?
Go the other way by using one kilocalorie equals 4.184 kilojoules. You can also press the swap button in the converter above to flip the direction in one click.
Is this kilojoule to kilocalorie converter accurate?
Yes. It uses internationally defined SI conversion factors, as maintained by the BIPM, and all math runs in your browser so nothing is rounded away on a server. For everyday use the displayed precision is more than enough.