Joules (J) to Kilocalories (kcal) Conversion
Joules
The joule (J) is the SI derived unit of energy, work, and heat, defined as the work done when a force of one newton displaces an object by one metre (J = N·m = kg·m²·s⁻²). Named after James Prescott Joule, who established the mechanical equivalent of heat in the 1840s, the joule unifies all forms of energy — mechanical, thermal, electrical, chemical, and nuclear — under one framework. One joule is small: lifting an apple (≈100 g) one metre requires about 1 joule, while a human at rest metabolises approximately 80 joules per second.
Kilocalories
The kilocalorie (kcal), commonly called a "Calorie" (capital C) in nutritional contexts, is a unit of energy equal to exactly 4,184 joules. It represents the energy needed to raise 1 kg of water by 1 °C. In nutrition, all food energy values are expressed in kcal per gram: carbohydrates and protein provide 4 kcal/g; fat provides 9 kcal/g; alcohol provides 7 kcal/g. An average adult requires approximately 2,000–2,500 kcal per day to maintain body weight.
| Joules (J) | Kilocalories (kcal) |
|---|---|
| 0.1 J | 0.0000239 kcal |
| 1 J | 0.000239 kcal |
| 2 J | 0.000478 kcal |
| 3 J | 0.000717 kcal |
| 5 J | 0.0012 kcal |
| 10 J | 0.00239 kcal |
| 20 J | 0.00478 kcal |
| 30 J | 0.00717 kcal |
| 50 J | 0.012 kcal |
| 100 J | 0.0239 kcal |
| 1000 J | 0.239 kcal |
Frequently Asked Questions (FAQ)
How many kilocalories are in 1 joules?
1 joules (J) is exactly 0.000239 kilocalories (kcal).
How do I convert joules to kilocalories?
Multiply the value in joules by 0.000239 to get the result in kilocalories. Or use the converter above — type any number and see the result instantly.