Unit Converter
Kilocalories to Kilojoules Converter
Convert kilocalories to kilojoules instantly. 1 kcal = 4.184 kJ. Use our free, precise energy unit converter online.
Kilojoules
4.184 kJ
1 kcal = 4.184 kJ
Kilocalories to Kilojoules formula
kJ = kcal × 4.184The kilocalorie (kcal) and kilojoule (kJ) both measure energy content. The conversion factor 4.184 comes from the definition of the calorie itself: one calorie equals approximately 4.184 joules of energy. This relationship is fundamental in physics and used universally in nutrition, chemistry, and engineering.
Kilocalories to Kilojoules conversion table
| Kilocalories (kcal) | Kilojoules (kJ) |
|---|---|
| 1 kcal | 4.184 kJ |
| 2 kcal | 8.368 kJ |
| 5 kcal | 20.92 kJ |
| 10 kcal | 41.84 kJ |
| 20 kcal | 83.68 kJ |
| 50 kcal | 209.2 kJ |
| 100 kcal | 418.4 kJ |
| 200 kcal | 836.8 kJ |
| 500 kcal | 2092 kJ |
| 1000 kcal | 4184 kJ |
When you need to convert kilocalories to kilojoules
- Nutrition: converting food energy labels from kcal (US/older) to kJ (metric/modern standard)
- Cooking: adjusting recipe energy values for different regional measurement systems
- Fitness tracking: converting burned calories from gym apps to scientific units
- Chemistry: standardizing experimental energy measurements across lab reports
- International nutrition: reading food packaging with both kcal and kJ listed
Frequently asked questions
Why is the conversion factor exactly 4.184?
The calorie was originally defined as the energy needed to raise 1 gram of water by 1°C. Modern science converted this to joules with the result that 1 calorie ≈ 4.184 joules. This precise factor is now the standard.
Is kcal the same as 'calories' on food labels?
Yes. Food labels use 'Calories' (capital C) or 'kcal' interchangeably. One food Calorie equals one kilocalorie. Always multiply food Calories by 4.184 to get kilojoules.
Which unit is more scientific?
The joule (and kilojoule) is the SI standard unit. Calories remain common in nutrition and food labeling, especially in North America. Scientists prefer kJ for consistency.