Convert Calories to Joules
One calorie equals 4.184 joules. Type any value to convert calories to joules instantly — with a full reference table below.
Convert Calories to Joules
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How to convert Calories to Joules
To convert calories to joules, multiply by 4.184. One calorie equals 4.184 J, and one joule equals 0.239006 cal.
- Take the value in calories — for example 7.5 cal.
- Multiply by 4.184 (the number of joules in one calorie).
- 7.5 × 4.184 = 31.38 J.
Quick mental estimate: Multiply the number of calories by 4.2 (within 0.4% of the exact answer).
Calories to Joules conversion table
| Calories | Joules |
|---|---|
| 1 cal | 4.184 J |
| 2 cal | 8.368 J |
| 5 cal | 20.92 J |
| 10 cal | 41.84 J |
| 20 cal | 83.68 J |
| 50 cal | 209.2 J |
| 100 cal | 418.4 J |
| 200 cal | 836.8 J |
| 500 cal | 2,092 J |
| 1,000 cal | 4,184 J |
| 2,000 cal | 8,368 J |
| Joules | Calories |
|---|---|
| 1 J | 0.239006 cal |
| 2 J | 0.478011 cal |
| 5 J | 1.195029 cal |
| 10 J | 2.390057 cal |
| 20 J | 4.780115 cal |
| 50 J | 11.95029 cal |
| 100 J | 23.90057 cal |
| 200 J | 47.80115 cal |
| 500 J | 119.5029 cal |
| 1,000 J | 239.0057 cal |
| 2,000 J | 478.0115 cal |
About converting Calories to Joules
Calories (cal) and Joules (J) are both units of energy. The exact factor is 1 cal = 4.184 J, so multiply by 4.184 to go from calories to joules (or divide to go back).
The conversion runs entirely in your browser. Need the reverse? Use the Joules to Calories converter, or the full unit converter for every unit at once.
Real-world energy in calories and joules
| Example | Calories | Joules |
|---|---|---|
| One food Calorie (kcal) | 1,000 cal | 4,184 J |
| A 100 W bulb running for one hour | 86,042.07 cal | 360,000 J |
| A smartphone battery (≈19 Wh) | ≈ 16,563.1 cal | ≈ 69,300 J |
“≈” 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.
The SI unit of energy: the work done by one newton over one metre.
Used for: Science and food labels (kJ).
The thermochemical calorie is exactly 4.184 J and a kilowatt-hour is exactly 3.6 MJ, so these factors are exact.