Calories ↔ Kilojoules
Convert between calories and kilojoules
Calories ↔ Kilojoules
Quick Facts
- •1 kcal = 4.184 kJ
- •2,000 kcal = 8,368 kJ (average daily intake)
- •Australia and NZ use kJ on food labels
- •Quick estimate: kJ ÷ 4.2 ≈ kcal
Calories and Kilojoules
Food energy is measured in kilocalories (kcal, commonly called 'Calories' with a capital C) in the US, and kilojoules (kJ) in Australia, Europe, and most other countries. One calorie equals 4.184 kilojoules. Food labels in many countries show both units.
Daily Energy Needs
The average adult needs about 2,000 kcal (8,368 kJ) per day. This varies based on age, sex, weight, and activity level. When reading international nutrition labels, divide kJ by 4.184 to get kcal, or multiply kcal by 4.2 for a quick kJ estimate.
How to convert Calories to Kilojoules
To convert calories to kilojoules, multiply the number of calories by the conversion factor. The exact factor is 4.184.
Formula
Kilojoules = Calories × 4.184
Worked example
Convert 10 kcal to kJ: 10 kcal = 41.84 kJ.
Calories to Kilojoules reference table
Use this quick lookup for common calories to kilojoules values.
| Calories (kcal) | Kilojoules (kJ) |
|---|---|
| 1 kcal | 4.18 kJ |
| 2 kcal | 8.37 kJ |
| 5 kcal | 20.92 kJ |
| 10 kcal | 41.84 kJ |
| 20 kcal | 83.68 kJ |
| 25 kcal | 104.6 kJ |
| 50 kcal | 209.2 kJ |
| 75 kcal | 313.8 kJ |
| 100 kcal | 418.4 kJ |
| 250 kcal | 1,046 kJ |
Frequently asked questions
What is the formula to convert Calories to Kilojoules?
Multiply the number of calories by 4.184 to get kilojoules. For example, 10 kcal equals 41.84 kJ.
How many kilojoules are in 1 calorie?
1 kcal equals 4.18 kJ.
How do I convert kilojoules back to calories?
Reverse the formula: Calories = Kilojoules ÷ 4.184. For example, 100 kJ equals 23.9 kcal.
Is this Calories to Kilojoules converter accurate?
Yes. Conversions use the internationally accepted ratio for calories and kilojoules and are calculated to 2 decimal places in your browser.
What is 10 kcal in kJ?
10 kcal equals 41.84 kJ.
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This calculator is for educational and reference purposes only. Always verify critical calculations independently.