cal to J (Calories → Joules)
1. Core Idea
The small calorie (cal) is an older heat unit; the joule (J) is SI energy. 1 cal = 4.184 J exactly (thermochemical). Multiply calories by 4.184 to get joules.
2. Formula
J = cal × 4.184
cal = J ÷ 4.184
(Do not confuse with dietary Calorie = kilocalorie.)
3. Quick Values
- 1 cal → 4.184 J
- 10 cal → 41.84 J
- 25 cal → 104.6 J
- 50 cal → 209.2 J
- 100 cal → 418.4 J
- 250 cal → 1,046 J
- 500 cal → 2,092 J
- 1,000 cal → 4,184 J
4. 3-Step Example
Convert 320 cal to J
- Formula: J = cal × 4.184
- Insert: 320 × 4.184
- = 1,338.88 ≈ 1.34 × 10³ J
5. Where It’s Used
Calorimetry, heat capacity labs, thermochemistry tables, small-scale thermal experiments, education.
6. Accuracy & Tips
- Diet labels use kcal (sometimes written Cal).
- Round to 3–4 sig figs unless high-precision.
- Energy in chemistry commonly reported in kJ; divide joules by 1000 if needed.
- Historical “15 °C calorie” differs slightly (4.1855 J) but rarely needed.
7. More Examples
| cal | J |
|---|---|
| 0.5 | 2.092 |
| 2 | 8.368 |
| 12 | 50.208 |
| 75 | 313.8 |
8. FAQ
Is this the food Calorie?
No. Food “Calorie” = 1 kilocalorie = 1000 small calories.
Why exactly 4.184?
Defined thermochemical value adopted for consistency; replaces older slightly different heat definitions.