Convert Calories to Kilojoules
One calorie equals 0.004184 kilojoules. Type any value to convert calories to kilojoules instantly — with a full reference table below.
Convert Calories to Kilojoules
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How to convert Calories to Kilojoules
To convert calories to kilojoules, multiply by 0.004184. One calorie equals 0.004184 kJ, and one kilojoule equals 239.0057 cal.
- Take the value in calories — for example 7.5 cal.
- Multiply by 0.004184 (the number of kilojoules in one calorie).
- 7.5 × 0.004184 = 0.03138 kJ.
Quick mental estimate: Divide the number of calories by 239 (accurate to better than 0.05%).
Calories to Kilojoules conversion table
| Calories | Kilojoules |
|---|---|
| 1 cal | 0.004184 kJ |
| 2 cal | 0.008368 kJ |
| 5 cal | 0.02092 kJ |
| 10 cal | 0.04184 kJ |
| 20 cal | 0.08368 kJ |
| 50 cal | 0.2092 kJ |
| 100 cal | 0.4184 kJ |
| 200 cal | 0.8368 kJ |
| 500 cal | 2.092 kJ |
| 1,000 cal | 4.184 kJ |
| 2,000 cal | 8.368 kJ |
| Kilojoules | Calories |
|---|---|
| 1 kJ | 239.0057 cal |
| 2 kJ | 478.0115 cal |
| 5 kJ | 1,195.029 cal |
| 10 kJ | 2,390.057 cal |
| 20 kJ | 4,780.115 cal |
| 50 kJ | 11,950.29 cal |
| 100 kJ | 23,900.57 cal |
| 200 kJ | 47,801.15 cal |
| 500 kJ | 119,502.9 cal |
| 1,000 kJ | 239,005.7 cal |
| 2,000 kJ | 478,011.5 cal |
About converting Calories to Kilojoules
Calories (cal) and Kilojoules (kJ) are both units of energy. The exact factor is 1 cal = 0.004184 kJ, so multiply by 0.004184 to go from calories to kilojoules (or divide to go back).
The conversion runs entirely in your browser. Need the reverse? Use the Kilojoules to Calories converter, or the full unit converter for every unit at once.
Real-world energy in calories and kilojoules
| Example | Calories | Kilojoules |
|---|---|---|
| One food Calorie (kcal) | 1,000 cal | 4.184 kJ |
| A 100 W bulb running for one hour | 86,042.07 cal | 360 kJ |
| A smartphone battery (≈19 Wh) | ≈ 16,563.1 cal | ≈ 69.3 kJ |
| One kilowatt-hour | 860,420.7 cal | 3,600 kJ |
“≈” marks typical values; the rest are defined or measured figures.
The units
The thermochemical calorie: exactly 4.184 J — energy to warm 1 g of water by about 1 °C.
Used for: Chemistry. Food 'Calories' are kilocalories.
1,000 joules.
Used for: Food energy on labels in Australia and the EU.
The thermochemical calorie is exactly 4.184 J and a kilowatt-hour is exactly 3.6 MJ, so these factors are exact.