Skip to main content

Joule to Calorie Converter

Convert joule calorie between units instantly. Includes conversion tables, common equivalents, and calculation formulas.

Reviewed by Manoj Kumar, Mathematics Educator

Reviewed by Manoj Kumar, Mathematics Educator

Formula

Calories = Joules / 4.1868 | Joules = Calories x 4.1868

The conversion between joules and calories is based on the thermochemical calorie definition where 1 cal = 4.1868 J exactly. This tool uses joules as the base unit and converts through multiplication or division of the appropriate conversion factor. All other energy units (BTU, Wh, eV) are similarly defined relative to the joule.

Worked Examples

Example 1: Food Energy Conversion

Problem:A meal contains 2,500 kcal (food Calories). How many kilojoules is this?

Solution:Convert kcal to J: 2,500 x 4,186.8 = 10,467,000 J\nConvert to kJ: 10,467,000 / 1,000 = 10,467 kJ\nConvert to MJ: 10,467 / 1,000 = 10.467 MJ

Result:2,500 kcal = 10,467 kJ = 10.467 MJ

Example 2: Physics Energy Problem

Problem:A physics experiment releases 5,000 joules. Express in calories and BTU.

Solution:To calories: 5,000 / 4.1868 = 1,194.2 cal\nTo kcal: 1,194.2 / 1,000 = 1.194 kcal\nTo BTU: 5,000 / 1,055.0559 = 4.739 BTU

Result:5,000 J = 1,194.2 cal = 1.194 kcal = 4.739 BTU

Frequently Asked Questions

How many calories are in one joule?

One joule equals approximately 0.2388 calories (thermochemical). Conversely, one calorie equals 4.1868 joules. This relationship comes from the definition of the thermochemical calorie as the energy needed to raise 1 gram of water by 1 degree Celsius. The joule is the SI unit of energy defined as the work done by a force of 1 newton through 1 meter.

What is the difference between a calorie and a Calorie (kilocalorie)?

A small calorie (cal) is the energy to raise 1 gram of water by 1 degree Celsius, while a large Calorie (Cal) or kilocalorie (kcal) is 1,000 small calories. Food labels use Calories (capital C), which are actually kilocalories. So when a food label says 200 Calories, it means 200 kcal or 200,000 small calories, which equals 836,800 joules or 836.8 kJ.

References

Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy