Convert Calories to Joules
1 calorie is 4.184 J. One calorie is exactly 4.184 joules.
One calorie is 4.184 joules. To convert calories to joules, multiply by 4.184; to go the other way, divide by 4.184 or multiply by 0.23900574. The factor is exact rather than rounded: it follows from NIST Special Publication 811. The thermochemical calorie: exactly 4.184 joules by definition.
Factor checked against the defining standard · How we check
- Calories × 4.184
value * 4.1844.184 J
1 calorie in every energy unit
| Unit | Value | Exact factor |
|---|---|---|
| joules | 4.184 J | × 4.184 |
| kilojoules | 0.004184 kJ | × 0.004184 |
| calories (as entered) | 1 cal | — |
| kilocalories | 0.001 kcal | × 0.001 |
| watt-hours | 0.001162222222 Wh | × 0.00116222222222 |
| kilowatt-hours | 0.000001162222222 kWh | × 0.00000116222222222 |
| British thermal units | 0.003965666831 BTU | × 0.00396566683139 |
| foot-pounds | 3.085960033 ft·lbf | × 3.08596003258 |
Factors are entered by hand from NIST Special Publication 811 rather than derived from a units library, so the ones that terminate are exact rather than rounded.
How do you convert calories to joules?
- 1.Take the measurement in calories.
- 2.Multiply by 4.184 — that is how many joules fit in one calorie.
- 3.To go back the other way, divide by 4.184, or multiply by 0.23900574.
Worked example: 25 calories to joules
- Formula
- cal × 4.184 = J
- Arithmetic
- 25 × 4.184 = 104.6 J
- Answer
- 25 cal = 104.6 J
The factor is exact, so this figure is exact too — only the display is rounded.
Calories to joules conversion table
| Calories | Joules |
|---|---|
| 1 cal | 4.184 J |
| 2 cal | 8.368 J |
| 3 cal | 12.552 J |
| 4 cal | 16.736 J |
| 5 cal | 20.92 J |
| 6 cal | 25.104 J |
| 7 cal | 29.288 J |
| 8 cal | 33.472 J |
| 9 cal | 37.656 J |
| 10 cal | 41.84 J |
| 12 cal | 50.208 J |
| 15 cal | 62.76 J |
| 20 cal | 83.68 J |
| 25 cal | 104.6 J |
| 50 cal | 209.2 J |
| 100 cal | 418.4 J |
| 200 cal | 836.8 J |
| 300 cal | 1,255.2 J |
| 500 cal | 2,092 J |
| 1000 cal | 4,184 J |
| 2000 cal | 8,368 J |
| 5000 cal | 20,920 J |
| 10000 cal | 41,840 J |
What is a calorie?
The thermochemical calorie: exactly 4.184 joules by definition. This is the small calorie — the one on a food label is a thousand of these, which is the single most common confusion in this group.
What is a joule?
The SI unit: one newton acting through one metre. Dropping a small apple one metre releases about one joule.
How many joules are in a calorie?
One calorie is 4.184 joules, exactly. Going the other way, one joule is 0.23900574 calories. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every energy unit here
| Unit | Symbol | One of these is |
|---|---|---|
| Joules | J | the base unit |
| Kilojoules | kJ | 1000 joule |
| Calories | cal | 4.184 joule |
| Kilocalories | kcal | 4184 joule |
| Watt-hours | Wh | 3600 joule |
| Kilowatt-hours | kWh | 3600000 joule |
| British thermal units | BTU | 1055.0559 joule |
| Foot-pounds | ft·lbf | 1.3558179 joule |
Source: NIST Special Publication 811 — the thermochemical calorie is exactly 4.184 J
Questions people actually ask
- How many joules are in a calorie?
- 4.184. The SI unit: one newton acting through one metre. Dropping a small apple one metre releases about one joule.
- How do I convert joules back to calories?
- Divide by 4.184, or multiply by 0.23900574 — they are the same operation.
Other energy conversions
Joules to calories — the same conversion the other way.