Calories to Joules Converter

To convert a measurement in calories to joules, multiply the value by 4.184. The conversion factor comes from the relationship between both units and the joule.

For example, to convert 5 cal to joules: 5 × 4.184 = 20.92 J.

A calorie (small calorie) is the energy needed to raise the temperature of one gram of water by one degree Celsius, defined as exactly 4.184 joules. The calorie originated in early-19th-century thermodynamics. The thermochemical calorie, fixed at exactly 4.184 J, is the modern standard, though it is often confused with the larger food Calorie (kilocalorie).

Common uses of calories include: Chemistry and thermodynamics; Heat-of-reaction measurements; Physics heat-transfer problems; Historical energy references.

A joule is the SI derived unit of energy, equal to the work done when a force of one newton moves an object one meter (1 N·m). Named after the English physicist James Prescott Joule, who established the mechanical equivalent of heat in the 1840s. The joule became the SI standard for all forms of energy, work, and heat.

Common uses of joules include: Scientific and engineering energy calculations; Nutrition labeling in metric countries; Mechanical work and kinetic energy; Electrical energy in physics (watt-seconds).

Chemistry and physics students bridge these units constantly. Heat-of-reaction and specific-heat problems are often set up in calories but answered in the SI joule, so knowing that one calorie is exactly 4.184 joules keeps calorimetry calculations correct.

Here are some common values converted:

1 cal = 4.184 J 5 cal = 20.92 J 10 cal = 41.84 J 50 cal = 209.2 J 100 cal = 418.4 J