Tool · Nutrition
Convert kJ to kcal (and back)
Convert kilojoules to kilocalories — and the other way round. Type a value into either box and the other one updates straight away. The basis: 1 kcal = 4.184 kJ.
Formula: kcal = kJ ÷ 4.184 · kJ = kcal × 4.184. Calculated in your browser.
The formula: kJ to kcal (and back)
Kilojoules (kJ) are the international SI unit for energy; kilocalories (kcal) are the unit most people are used to. The conversion factor is fixed:
- kJ → kcal: value ÷ 4.184 (e.g. 1,000 kJ ÷ 4.184 = 239 kcal)
- kcal → kJ: value × 4.184 (e.g. 234 kcal × 4.184 = 979 kJ)
What are kJ and kcal — and what is the difference?
Both units measure the same thing: energy. They differ only in scale and in where they come from.
- Kilojoule (kJ) is the legal SI unit for energy. One joule is the energy a force of one newton does over one metre; a kilojoule is 1,000 joules.
- Kilocalorie (kcal) is the older unit from nutrition science. One kilocalorie is 1,000 calories (cal) — and when people say “calories” in everyday life, they almost always mean kilocalories.
kJ or kcal — which is better? Neither is more precise. A label has to carry both anyway, and if you are doing your own sums, stick to one unit throughout.
Why do food labels show kJ and kcal?
Anyone labelling a food has to give the energy value in both units. Annex XV of Regulation (EU) No 1169/2011 sets the order as kJ first, then kcal — so for example “Energy 979 kJ / 234 kcal”. That is why converting between the two is everyday work when you make labels.
Want to calculate the energy value from a recipe rather than just convert it? That is what Foodlex does — the full nutrition declaration straight from your ingredients.
Conversion table kJ → kcal
| Kilojoules | Kilocalories (rounded) |
|---|---|
| 100 kJ | 24 kcal |
| 200 kJ | 48 kcal |
| 300 kJ | 72 kcal |
| 400 kJ | 96 kcal |
| 500 kJ | 120 kcal |
| 600 kJ | 143 kcal |
| 700 kJ | 167 kcal |
| 800 kJ | 191 kcal |
| 900 kJ | 215 kcal |
| 1,000 kJ | 239 kcal |
| 1,100 kJ | 263 kcal |
| 1,200 kJ | 287 kcal |
| 1,300 kJ | 311 kcal |
| 1,400 kJ | 335 kcal |
| 1,500 kJ | 359 kcal |
| 1,600 kJ | 382 kcal |
| 1,700 kJ | 406 kcal |
| 1,800 kJ | 430 kcal |
| 1,900 kJ | 454 kcal |
| 2,000 kJ | 478 kcal |
| 2,100 kJ | 502 kcal |
| 2,200 kJ | 526 kcal |
| 2,300 kJ | 550 kcal |
| 2,400 kJ | 574 kcal |
| 2,500 kJ | 598 kcal |
| 2,600 kJ | 621 kcal |
| 2,700 kJ | 645 kcal |
| 2,800 kJ | 669 kcal |
| 2,900 kJ | 693 kcal |
| 3,000 kJ | 717 kcal |
| 3,500 kJ | 837 kcal |
| 4,000 kJ | 956 kcal |
| 4,184 kJ | 1,000 kcal |
Conversion table kcal → kJ
| Kilocalories | Kilojoules (rounded) |
|---|---|
| 50 kcal | 209 kJ |
| 100 kcal | 418 kJ |
| 150 kcal | 628 kJ |
| 200 kcal | 837 kJ |
| 250 kcal | 1,046 kJ |
| 300 kcal | 1,255 kJ |
| 350 kcal | 1,464 kJ |
| 400 kcal | 1,674 kJ |
| 450 kcal | 1,883 kJ |
| 500 kcal | 2,092 kJ |
| 550 kcal | 2,301 kJ |
| 600 kcal | 2,510 kJ |
| 650 kcal | 2,720 kJ |
| 700 kcal | 2,929 kJ |
| 750 kcal | 3,138 kJ |
| 800 kcal | 3,347 kJ |
| 850 kcal | 3,556 kJ |
| 900 kcal | 3,766 kJ |
| 950 kcal | 3,975 kJ |
| 1,000 kcal | 4,184 kJ |
Why the pack sometimes does not add up
Divide the kJ figure on a pack by 4.184 and you will not always land exactly on the kcal figure printed next to it. That is not a mistake by the manufacturer: the FIC Regulation does not convert the two values into each other — it calculates both separately from the same nutrient amounts. Annex XIV gives its own pair of factors for each nutrient:
| Nutrient | Kilojoules | Kilocalories |
|---|---|---|
| Carbohydrate (except polyols) | 17 kJ/g | 4 kcal/g |
| Polyols | 10 kJ/g | 2.4 kcal/g |
| Protein | 17 kJ/g | 4 kcal/g |
| Fat | 37 kJ/g | 9 kcal/g |
| Salatrims | 25 kJ/g | 6 kcal/g |
| Alcohol (ethanol) | 29 kJ/g | 7 kcal/g |
| Organic acid | 13 kJ/g | 3 kcal/g |
| Fibre | 8 kJ/g | 2 kcal/g |
| Erythritol | 0 kJ/g | 0 kcal/g |
These pairs are rounded and do not sit at a ratio of 4.184 to each other: for carbohydrate it is 17 ÷ 4 = 4.25, for fat 37 ÷ 9 = 4.11. Depending on what a product is made of, the ratio on the label therefore lands somewhere around 4.0 to 4.33 — so a difference of a few per cent against a straight conversion is normal.
For your own labelling that means: do not convert one energy figure into the other. Calculate both from the recipe.
Frequently asked questions
How do you convert kJ to kcal?
Divide by 4.184: kcal = kJ ÷ 4.184. The other way round, kJ = kcal × 4.184. Example: 1,000 kJ ÷ 4.184 = 239 kcal.
How much is 1 kJ in kcal?
One kilojoule is about 0.239 kcal. The other way round, one kilocalorie is 4.184 kJ.
Is a calorie the same as a kilocalorie?
In everyday speech yes, technically no. One kilocalorie is 1,000 calories. When people talk about the “calories” in a food they mean kilocalories — which is why the label says kcal.
Why do food labels show both units?
Because Annex XV of the FIC Regulation requires it. It sets out the units to be used in the nutrition declaration “for energy (kilojoules (kJ) and kilocalories (kcal))”, and gives the row as “energy kJ/kcal” — kJ first.
Does the factor 4.184 also apply to sport and fitness?
Yes, the conversion is the same everywhere. What differs is the reference: an exercise bike shows the work delivered in kJ, not the energy your body used — that is noticeably higher, because efficiency is below 100 %.
The factor 1 kcal = 4.184 kJ is the definition of the thermochemical kilocalorie, not a factor from the FIC Regulation. For calculating the energy value the Regulation prescribes the nutrient factors in Annex XIV instead (see the section above). Table values are rounded. Wording checked against the consolidated English text of Regulation (EU) No 1169/2011, CELEX 02011R1169-20180101. This page is not legal advice.