How to convert calories to kilojoules
kJ = cal × 0.004184Multiply the value in calories by 0.004184. To go the other way, multiply by 239.0057361 (or divide by 0.004184).
A calorie is smaller than a kilojoule: it takes 239.0057361 calories to make one kilojoule.
Worked examples
- 1 calorie (thermochemical)1 cal × 0.004184 = 0.004184 kJ
- 5 calories5 cal × 0.004184 = 0.02092 kJ
- 10 calories10 cal × 0.004184 = 0.04184 kJ
- 20 calories20 cal × 0.004184 = 0.08368 kJ
- 100 calories100 cal × 0.004184 = 0.4184 kJ
Calories to kilojoules conversion table
Values are calculated by the conversion engine and rounded to 8 significant figures.
| Calories (cal) | Kilojoules (kJ) |
|---|---|
| 0.1 cal | 0.0004184 kJ |
| 0.25 cal | 0.001046 kJ |
| 0.5 cal | 0.002092 kJ |
| 1 cal | 0.004184 kJ |
| 2 cal | 0.008368 kJ |
| 3 cal | 0.012552 kJ |
| 4 cal | 0.016736 kJ |
| 5 cal | 0.02092 kJ |
| 6 cal | 0.025104 kJ |
| 7 cal | 0.029288 kJ |
| 8 cal | 0.033472 kJ |
| 9 cal | 0.037656 kJ |
| 10 cal | 0.04184 kJ |
| Calories (cal) | Kilojoules (kJ) |
|---|---|
| 12 cal | 0.050208 kJ |
| 15 cal | 0.06276 kJ |
| 20 cal | 0.08368 kJ |
| 25 cal | 0.1046 kJ |
| 30 cal | 0.12552 kJ |
| 40 cal | 0.16736 kJ |
| 50 cal | 0.2092 kJ |
| 75 cal | 0.3138 kJ |
| 100 cal | 0.4184 kJ |
| 250 cal | 1.046 kJ |
| 500 cal | 2.092 kJ |
| 1,000 cal | 4.184 kJ |
About the units
Calorie (cal)
The “small” calorie: exactly 4.184 J (thermochemical definition), roughly the energy to heat one gram of water by 1 °C.
Kilojoule (kJ)
One thousand joules. Food labels in Australia and the EU list energy in kJ alongside kcal. One kilojoule equals 1,000 joules (J).
Frequently asked questions
How many kilojoules are in one calorie?
There are 0.004184 kilojoules in one calorie, and this value is exact by definition.
How do I convert calories to kilojoules?
Multiply the number of calories by 0.004184. For example, 10 cal × 0.004184 = 0.04184 kJ.
How many calories are in one kilojoule?
One kilojoule equals 239.0057361 calories. That is the reverse factor, 1 ÷ 0.004184.
What is 10 calories in kilojoules?
10 cal = 0.04184 kJ.
Is this cal to kJ converter accurate?
Yes. Both units are defined exactly in terms of SI units, so the conversion factor is exact; results are shown to 12 significant figures by default and you can change precision in the converter. Calculations run in your browser using the same tested engine that generated this page.