Calorie to Joule Converter (cal to J)
1 calorie equals 4.184 joules (J) — multiply the number of calories by 4.184 to convert. This uses the thermochemical calorie, defined as exactly 4.184 J, the standard factor in physics and chemistry.
The formula
Multiply calories by the exact factor 4.184:
J = cal × 4.184For example, 50 cal × 4.184 = 209.2 J. To reverse it, divide by 4.184 (or multiply by 0.23900574).
Conversion table
| Calories (cal) | Joules (J) |
|---|---|
| 1 | 4.184 |
| 2 | 8.368 |
| 5 | 20.92 |
| 10 | 41.84 |
| 25 | 104.6 |
| 50 | 209.2 |
| 100 | 418.4 |
| 500 | 2092 |
| 1000 | 4184 |
How to convert online
- Type the number of calories into the first box.
- Read the joule result instantly in the second box.
- Enter a joule value instead to convert back to calories — it works both ways.
Use the Calorie to Joule Converter — free and instant in your browser.
Where this conversion is used
The joule is the SI unit of energy, so science, engineering and thermodynamics work in joules while older heat and nutrition references use calories. Converting cal to J is needed when you rework a heat-of-reaction figure, standardise lab data, or bring a calorie-based measurement into SI units.
Scaling and accuracy
The conversion is linear, so you can scale any result: since 100 cal = 418.4 J, then 200 cal = 836.8 J and 1,000 cal = 4,184 J. Be aware there are two slightly different calories in use. This tool applies the thermochemical calorie of exactly 4.184 J, common in chemistry. The other, the international steam-table calorie, is 4.1868 J — a difference of under 0.1%, which rarely matters but can shift high-precision lab results. For food energy, remember the label Calorie is a kilocalorie, so a 250 Calorie snack is 250,000 small calories, or about 1,046,000 J.
FAQ
How many joules are in a calorie?
One calorie equals 4.184 J. Multiply calories by 4.184 — for example, 10 cal = 41.84 J.
Is this the small calorie or the food Calorie?
This is the small (thermochemical) calorie, cal. A food Calorie (kcal) is 1,000 of these, so 1 kcal = 4,184 J.
How do I convert joules back to calories?
Divide by 4.184, or multiply by 0.23900574. For instance, 100 J ≈ 23.9 cal.
Is the conversion exact?
Yes. The thermochemical calorie is defined as exactly 4.184 J, so the factor is exact.
Related converters
- Joule to Calorie Converter
- Calorie to Kilojoule Converter
- Calorie to Kilocalorie Converter
- Calorie to Watt-hour Converter
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