Calorie to Joule Converter
Converts calorie to joule (cal to J) and back. The conversion factor is shown below every result.
How to Convert Calorie to Joule
What Is a Calorie?
A calorie (cal), specifically the thermochemical calorie used in physics and chemistry, equals exactly 4.184 joules. It's the small calorie, not the food-label Calorie (kcal), which is 1,000 times larger.
What Is a Joule?
A joule (J), the SI energy unit, equals one newton-meter.
Common Calorie to Joule Reference Points
Real-world reference values for quick sanity checks.
| Item | Calorie (cal) | Joule (approx.) |
|---|---|---|
| Heating 1 g of water by 1°C | 1 cal | 4.184 J |
| A 100-Calorie food snack (100 kcal = 100,000 cal) | 100000 cal | 418,400 J |
| Reference values are illustrative approximations for common items, not measured specifications. | ||
Calorie to Joule Conversion Table
| Calorie (cal) | Joule (J) |
|---|---|
| 1 cal | 4.184 J |
| 10 cal | 41.84 J |
| 100 cal | 418.4 J |
| 1000 cal | 4184 J |
| 10000 cal | 41840 J |
| 100000 cal | 418400 J |
| Source: NIST SP 811, footnotes (1 cal = 4.184 J exactly, thermochemical calorie) | |
Frequently Asked Questions
How do I convert calories to joules?
Multiply the calorie value by 4.184. For example, 50 cal × 4.184 = 209.2 J.
Why is 4.184 the exact factor?
The thermochemical calorie was defined as exactly 4.184 joules by international scientific convention, replacing older, slightly inconsistent definitions based on the specific heat of water at various temperatures.
Should I use this page for nutrition label calories?
Only if you first convert food Calories (kcal) to small calories by multiplying by 1,000. Most nutrition contexts are better served by directly multiplying kcal by 4,184 to get joules, or 4.184 to get kilojoules.
Related Energy Converters
A good measuring tool marked in both cal and J removes the guesswork at the point of use.