Energy converter
Kilocalories to Kilojoules
Kilocalories and Kilojoules measure the same quantity in different unit systems. The relationship is 1 kcal = 4.184 kJ, which gives 4.184 kJ per kcal. Below you can convert any value, check a worked example and read the full chart.
Formula 1 kcal = 4.184 kJ
Need the other direction? Kilojoules to Kilocalories.
How to convert Kilocalories to Kilojoules
A kilocalorie is 4,184 joules and is the Calorie printed on food labels. A kilojoule is 1,000 joules and appears on nutrition labels in many countries.
To convert Kilocalories to Kilojoules, multiply the value in kcal by 4.184. For example, 10 kcal × 4.184 = 41.84 kJ. This works because the ratio between the two units is constant for every value in energy.
Worked examples
| kcal | kJ |
|---|---|
| 1 kcal | 4.184 kJ |
| 2.5 kcal | 10.46 kJ |
| 5 kcal | 20.92 kJ |
| 10 kcal | 41.84 kJ |
| 25 kcal | 104.6 kJ |
| 50 kcal | 209.2 kJ |
| 100 kcal | 418.4 kJ |
Reverse conversion
| kJ | kcal |
|---|---|
| 1 kJ | 0.23900574 kcal |
| 5 kJ | 1.195029 kcal |
| 10 kJ | 2.390057 kcal |
| 25 kJ | 5.975143 kcal |
| 50 kJ | 11.950287 kcal |
| 100 kJ | 23.900574 kcal |
When this conversion is useful
This is the calculation you need when you are comparing a nutrition label, an electricity bill or a heating system. Because the factor is fixed, you can use the same number for a single measurement or for a batch: 1,000 kcal is 4,184 kJ.
Is the conversion exact?
Yes for practical use: the factors come from international definitions, with rounding applied only for display.
Reference: BIPM SI Brochure and NIST SP 811. Last reviewed: 2026-11-01.
kcal to kJ conversion chart
The chart lists the most requested values. For a value that is not here, use the converter at the top of the page.
| Kilocalories (kcal) | Kilojoules (kJ) |
|---|---|
| 1 kcal | 4.184 kJ |
| 2 kcal | 8.368 kJ |
| 3 kcal | 12.552 kJ |
| 4 kcal | 16.736 kJ |
| 5 kcal | 20.92 kJ |
| 6 kcal | 25.104 kJ |
| 7 kcal | 29.288 kJ |
| 8 kcal | 33.472 kJ |
| 9 kcal | 37.656 kJ |
| 10 kcal | 41.84 kJ |
| 11 kcal | 46.024 kJ |
| 12 kcal | 50.208 kJ |
| 13 kcal | 54.392 kJ |
| 14 kcal | 58.576 kJ |
| 15 kcal | 62.76 kJ |
| 16 kcal | 66.944 kJ |
| 17 kcal | 71.128 kJ |
| 18 kcal | 75.312 kJ |
| 19 kcal | 79.496 kJ |
| 20 kcal | 83.68 kJ |
| 21 kcal | 87.864 kJ |
| 22 kcal | 92.048 kJ |
| 23 kcal | 96.232 kJ |
| 24 kcal | 100.416 kJ |
| 25 kcal | 104.6 kJ |
| 26 kcal | 108.784 kJ |
| 27 kcal | 112.968 kJ |
| 28 kcal | 117.152 kJ |
| 29 kcal | 121.336 kJ |
| 30 kcal | 125.52 kJ |
| 31 kcal | 129.704 kJ |
| 32 kcal | 133.888 kJ |
| 33 kcal | 138.072 kJ |
| 34 kcal | 142.256 kJ |
| 35 kcal | 146.44 kJ |
| 36 kcal | 150.624 kJ |
| 37 kcal | 154.808 kJ |
| 38 kcal | 158.992 kJ |
| 39 kcal | 163.176 kJ |
| 40 kcal | 167.36 kJ |
| 41 kcal | 171.544 kJ |
| 42 kcal | 175.728 kJ |
| 43 kcal | 179.912 kJ |
| 44 kcal | 184.096 kJ |
| 45 kcal | 188.28 kJ |
| 46 kcal | 192.464 kJ |
| 47 kcal | 196.648 kJ |
| 48 kcal | 200.832 kJ |
| 49 kcal | 205.016 kJ |
| 50 kcal | 209.2 kJ |
| 60 kcal | 251.04 kJ |
| 70 kcal | 292.88 kJ |
| 80 kcal | 334.72 kJ |
| 90 kcal | 376.56 kJ |
| 100 kcal | 418.4 kJ |
Frequently asked questions
How many Kilojoules are in 1 Kilocalories?
1 kcal equals 4.184 kJ.
How do I convert Kilocalories to Kilojoules?
Multiply the kcal value by 4.184. Example: 25 kcal = 104.6 kJ.
What is 2.5 kcal in kJ?
2.5 kcal = 10.46 kJ.
Is the kcal to kJ conversion exact?
Yes for practical use: the factors come from international definitions, with rounding applied only for display.
Does the calculator work offline?
Yes. The conversion runs in your browser with JavaScript, so it works after the page has loaded, even without a connection.