Calories to Joules Converter
Convert calories to joules instantly. Enter calories or food Calories (kcal) to get joules using the 4.184 factor, with the reverse direction shown.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Calories to Joules Converter Works
This tool converts calories to joules (J) and back. The joule is the SI unit of energy, while calories are still widely used in nutrition and chemistry. You can choose the small calorie (cal) or the food Calorie (kcal), since they differ by a factor of 1000.
The Formula
Joules = small calories × 4.184 Joules = food Calories (kcal) × 4,184
The thermochemical calorie is defined as exactly 4.184 joules. A food Calorie is 1000 of these, so it equals 4,184 J.
Worked Example
Convert 500 small calories to joules:
- Joules = 500 × 4.184 = 2,092 J
A 200 Calorie (kcal) snack:
- Joules = 200 × 4,184 = 836,800 J (836.8 kJ)
Going the other way, 10,000 J in small calories:
- cal = 10,000 ÷ 4.184 = 2,390.1 cal
Calories to Joules Quick Reference
| Calories | Joules |
|---|---|
| 1 cal | 4.184 |
| 100 cal | 418.4 |
| 1 kcal | 4,184 |
| 200 kcal | 836,800 |
| 2000 kcal | 8,368,000 |
Small Calorie vs Food Calorie
The biggest source of confusion is the two “calories”. The small calorie (cal) is a physics and chemistry unit equal to 4.184 J. The food Calorie (kcal), written with a capital C on labels, is 1000 times larger at 4,184 J. A “2,000 calorie” diet really means 2,000 kilocalories, or about 8.4 megajoules. This converter lets you pick the right one so your result matches the source.
Frequently asked questions
How many joules are in a calorie?+
One small calorie equals 4.184 joules. One food Calorie (kilocalorie) equals 4,184 joules. To convert calories to joules, multiply by 4.184.
How do I convert calories to joules?+
Multiply the calorie value by 4.184. For food Calories (kcal), multiply by 4,184 instead. For example, 500 cal × 4.184 = 2,092 J, while 500 kcal = 2,092,000 J.
What is the difference between a calorie and a Calorie?+
A lowercase calorie is the small calorie, the energy to heat 1 gram of water by 1 °C, equal to 4.184 J. A capital Calorie used on food labels is a kilocalorie, equal to 1000 small calories or 4,184 J.
How many joules is a 200 Calorie snack?+
A 200 food Calorie (kcal) snack contains about 836,800 joules, or 836.8 kilojoules. Food labels in many countries list this directly as kJ.
Which calorie definition does this use?+
It uses the thermochemical calorie of exactly 4.184 joules, the standard for nutrition and chemistry. You can choose small calorie or food Calorie (kcal) in the converter.