How to convert calories to joules
Apply the documented calories-to-joules relationship below, keeping the full stored constant until the displayed result is rounded.
Calories × 4.184 = Joules
For example, 10 cal equals 41.84 J.
Calories to Joules reference table
| Calories | Joules |
|---|---|
| 1 cal | 4.184 J |
| 5 cal | 20.92 J |
| 10 cal | 41.84 J |
| 25 cal | 104.6 J |
| 50 cal | 209.2 J |
| 100 cal | 418.4 J |
Method and quality checks
- Calculation
- Calories × 4.184 = Joules. The calculator keeps the stored factor through the operation and rounds only the displayed result to the selected or page-supported precision.
- Unit convention
- The named energy convention is used exactly as labelled. Small calories, food Calories, and alternate BTU definitions must not be mixed.
- Input validation
- Finite numeric inputs are accepted. Results outside the supported numeric range are rejected instead of being displayed as valid measurements.
- Reasonableness check
- 10 cal produces 41.84 J. Check the direction and approximate scale before relying on a more precise displayed value.
Deeper method: How significant figures work.
Thermochemical calories converted to joules
This page converts small thermochemical calories, where 1 cal = 4.184 J exactly. Nutrition labels use kilocalories—often displayed as Calories—so a nutrition value requires a factor 1,000 times larger.
- Confirm whether the source says cal, kcal, or Calories.
- Use 4,184 joules per food Calorie.
- Scientific sources may identify a specific calorie definition; preserve that convention.
Reference: NIST energy conversion factors.