Quick answer
1 calorie (kcal) = 4.184 kJ. To convert calories to kJ, multiply the calories by 4.184. For example, 250 calories × 4.184 = 1,046 kJ, and a 2,000 calorie day is 8,368 kJ.
How to convert cal to kJ
- Take the energy in calories (kcal) from your label, app or meal plan.
- Multiply it by 4.184.
- The answer is the energy in kilojoules (kJ).
| Calories | Working | Kilojoules |
|---|---|---|
| 100 kcal | 100 × 4.184 | 418.4 kJ |
| 250 kcal | 250 × 4.184 | 1,046 kJ |
| 500 kcal | 500 × 4.184 | 2,092 kJ |
| 2,000 kcal | 2000 × 4.184 | 8,368 kJ |
Calories to kJ conversion table
| Calories (kcal) | Kilojoules (kJ) | Joules (J) |
|---|---|---|
| 50 kcal | 209.2 kJ | 209,200 J |
| 100 kcal | 418.4 kJ | 418,400 J |
| 200 kcal | 836.8 kJ | 836,800 J |
| 250 kcal | 1,046 kJ | 1,046,000 J |
| 500 kcal | 2,092 kJ | 2,092,000 J |
| 1,000 kcal | 4,184 kJ | 4,184,000 J |
| 1,500 kcal | 6,276 kJ | 6,276,000 J |
| 2,000 kcal | 8,368 kJ | 8,368,000 J |
| 2,500 kcal | 10,460 kJ | 10,460,000 J |
The calories to kJ chart has a longer list, from 1 to 5,000 kcal.
Cal to kJ: which "calorie" are you converting?
Nearly everyone who searches for calories to kj means food calories, also called kilocalories (kcal) or Calories with a capital C. That is the unit this converter uses when you choose "Calories (kcal)".
The small calorie, written cal, is 1,000 times smaller: 1 cal = 4.184 joules = 0.004184 kJ. Choose "Small calories (cal)" in the drop-down if your source really means the small unit, as in a chemistry problem. If you are unsure, check the size of the number: a snack of "250 cal" on a food label is 250 kcal, not 250 small calories.
Other ways to write calories to kJ
The same conversion is searched as cal to kj, cals to kj, cals to kjs, calorie to kj, or calories to kj. Some people write cal to kjoules, or ask for the calorie to kj conversion or cal to kj conversion. Others look for a cal to kj converter, calorie to kj converter, calorie to kj calculator, calorie kj converter, or a calories and kj converter that works in both directions. You might also see convert cal to kj, convert calorie to kj, calories converted to kj, cal kj, or a calorie converter to kilojoules. They all use the same factor and all give the same result on this page.
When to convert calories to kJ
- Following a plan written in kcal while your labels show kJ. Convert your daily target once, then compare labels against that number.
- Comparing products from different countries. Australian and New Zealand labels lead with kJ, while US labels show Calories.
- Checking a recipe or app. Some nutrition apps let you choose the unit, while others do not.
For the reverse direction, use the KJ to Cal converter. To see what a typical day looks like, read how many kJ you should eat per day.
Frequently asked questions
How many kJ are in 1 calorie?
One calorie (kcal) is 4.184 kJ. One small calorie (cal) is 0.004184 kJ, which is 4.184 joules.
How do I convert calories to kJ?
Multiply the calories (kcal) by 4.184. For example, 500 kcal × 4.184 = 2,092 kJ.
How many kJ is 2,000 calories?
2,000 calories (kcal) is 8,368 kJ. See 2000 calories to kJ.
Are cal and kcal the same on a food label?
In practice, yes. On food labels "calories" or "Cal" almost always means kcal. Strictly speaking, a small-c cal is one thousandth of a kcal.
Why are kJ numbers bigger than calorie numbers?
A kilojoule is a smaller unit of energy than a kilocalorie, so the same amount of energy needs a bigger number. It takes 4.184 kJ to make 1 kcal.
Last updated 11 Oct 2026. How we calculate.