Kilocalories to Kilojoules
Convert kilocalorie to kilojoule instantly — type a value and read the result, with the exact formula shown.
Reviewed by the CalcCafe editorial team · Last updated 1 July 2026 · How we test our tools
Example
1 kcal = 4.184 kJ, 5 kcal = 20.92 kJ, 10 kcal = 41.84 kJ.
Common conversions: kilocalorie to kilojoule
Quick reference for the kcal → kJ values you are most likely to need, computed with the exact factor the converter above uses. It includes the specific values people most often look up (100 kcal, 1,000 kcal, 200 kcal, 405 kcal, 20 kcal).
| Kilocalorie (kcal) | Kilojoule (kJ) |
|---|
| 1 kcal | 4.184 kJ |
| 2 kcal | 8.368 kJ |
| 3 kcal | 12.552 kJ |
| 5 kcal | 20.92 kJ |
| 10 kcal | 41.84 kJ |
| 15 kcal | 62.76 kJ |
| 20 kcal | 83.68 kJ |
| 25 kcal | 104.6 kJ |
| 30 kcal | 125.52 kJ |
| 40 kcal | 167.36 kJ |
| 45 kcal | 188.28 kJ |
| 50 kcal | 209.2 kJ |
| 60 kcal | 251.04 kJ |
| 70 kcal | 292.88 kJ |
| 75 kcal | 313.8 kJ |
| 80 kcal | 334.72 kJ |
| 90 kcal | 376.56 kJ |
| 100 kcal | 418.4 kJ |
| 110 kcal | 460.24 kJ |
| 150 kcal | 627.6 kJ |
| 200 kcal | 836.8 kJ |
| 250 kcal | 1,046 kJ |
| 405 kcal | 1,694.52 kJ |
| 500 kcal | 2,092 kJ |
| 1,000 kcal | 4,184 kJ |
Kilojoule to Kilocalorie
| Kilojoule (kJ) | Kilocalorie (kcal) |
|---|
| 1 kJ | 0.239006 kcal |
| 5 kJ | 1.195 kcal |
| 10 kJ | 2.3901 kcal |
| 50 kJ | 11.9503 kcal |
| 100 kJ | 23.9006 kcal |
How it works
Kilojoule = Kilocalorie × 4.184. Every value is converted through a single joule base unit using internationally defined conversion factors, so any from/to pair stays consistent.
Good to know
Converting kilocalories to kilojoules is something most people run into when reading food labels. In the United States, energy on packaging is printed in "Calories" (which are really kilocalories), while Europe, Australia, and most of the rest of the world list energy in kilojoules — and many labels show both side by side. If you track your diet with an app set to metric units, or you're comparing an American product to one sold in the EU, this conversion turns one number into the other.
Both units measure the same thing — energy — but they come from different traditions. The calorie was originally defined around how much heat raises the temperature of water, while the joule is the SI (metric) unit of energy, named after physicist James Prescott Joule. Because a "dietary calorie" is actually 1,000 small calories (one kilocalorie), it lines up directly with the kilojoule, and the two are bridged by a single fixed factor.
The rule of thumb is simple: multiply kilocalories by roughly 4.2 to get kilojoules. So a 250 kcal snack is about 1,046 kJ, and a quick mental shortcut is "just over four times." To reverse it, divide kilojoules by 4.2. If you want to be precise, the exact factor is 4.184.
- The 4.184 figure is the thermochemical calorie, which nutrition labels worldwide use by international agreement — so this is an exact, not approximate, definition.
- Don't confuse the food Calorie (capital C, a kilocalorie) with the tiny physics calorie; a label's "120 Calories" means 120 kcal, which is 502 kJ, not 0.5 kJ.
Frequently asked questions
How do you convert kilocalorie to kilojoule?
Multiply the number of kilocalories by 4.184 to get kilojoules. For example, 1 kcal = 4.184 kJ.
What is 1 kilocalorie in kilojoules?
1 kilocalorie equals 4.184 kilojoules (1 kcal = 4.184 kJ).
How many kilocalories are in 1 kilojoule?
There are 0.2390057 kilocalories in 1 kilojoule.
Is this converter free and private?
Yes. It runs entirely in your browser, so your inputs never leave your device, there is no sign-up, and it works offline once loaded.
Are the conversions exact?
Conversions use internationally defined factors and are exact where the definitions are exact (for example, 1 inch = 2.54 cm). Displayed results are rounded for readability.
People also ask
How many kilojoules are in 100 kcal?
100 kilocalories equals 418.4 kilojoules. Multiply the kcal figure by 4.184 to get the answer.
Why do food labels show both kcal and kJ?
Many countries, including those in the EU and Australia, legally require energy to be listed in kilojoules as the official SI unit, while kcal is kept because consumers are familiar with it. Showing both lets shoppers in different regions read the label easily.
Is a kilocalorie the same as a food Calorie?
Yes. The 'Calorie' with a capital C on nutrition labels is a kilocalorie. So 200 Calories equals 200 kcal, which is 836.8 kJ.
What is 2000 kcal in kilojoules?
2000 kilocalories equals 8,368 kilojoules, since 2000 multiplied by 4.184 is 8,368. This is roughly the daily energy reference intake for an adult.
How do I convert kilojoules back to kilocalories?
Divide the number of kilojoules by 4.184. For example, 500 kJ divided by 4.184 equals about 119.5 kcal.
Why is the conversion factor 4.184 and not 4.2?
4.184 is the exact thermochemical calorie definition adopted internationally for nutrition. The value 4.2 is just a rounded version useful for quick mental math.
How many kJ is one slice of bread at about 80 kcal?
Around 80 kcal converts to roughly 335 kilojoules (80 multiplied by 4.184 equals 334.7 kJ).
Is kcal different from cal?
Yes, one kilocalorie is 1,000 small calories. The 'Calorie' on a food label (often written with a capital C) is actually a kilocalorie, so a 200 Calorie snack contains 200 kcal, or 200,000 cal. In kilojoules that snack is 200 × 4.184 = 836.8 kJ.
How much is 1000 calories in kJ?
If you mean 1,000 food Calories (kilocalories), that is 1,000 × 4.184 = 4,184 kJ. If you literally mean 1,000 small calories, it is just 4.184 kJ, because a kilocalorie is 1,000 times larger. Food and diet figures almost always mean kilocalories, so 4,184 kJ is usually the answer you want.
If I burn 900 calories a day, how much weight will I lose?
A common rule of thumb is that a deficit of about 3,500 kcal corresponds to roughly one pound (0.45 kg) of body fat, so a 900 kcal daily deficit adds up to 6,300 kcal a week, or about 1.8 lb (0.8 kg) per week in theory. In kilojoules, 900 kcal is 900 × 4.184 = 3,766 kJ. Real results vary because the body adapts and water weight fluctuates, and burning 900 kcal only creates a deficit if you do not eat it back. This is general information, not medical advice.
Why does Australia use kJ instead of calories?
Australia converted to the metric system in the 1970s, and the kilojoule is the SI unit of energy, so food labelling standards there require energy to be shown in kilojoules (kilocalories may be shown alongside). The same is true in New Zealand, while the EU requires both kJ and kcal. The conversion is the same everywhere: kilocalories × 4.184 = kilojoules, so a 2,000 kcal daily intake is 8,368 kJ.
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Sources & references
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