There are 4.18 joules in a single calorie. Both joules and calories are common measures of energy. Food is typically reported in kilocalories, which is equal to 1,000 calories.
A calorie is a unit of energy that measures how much energy is needed to increase the temperature of a single gram of water. The primary measure of energy, however, is the joule, which is equal to one newton-meter. It is the standard unit of energy in both the imperial and metric system. To convert a number of calories into joules, multiply the calories by 4.18. Similarly, a number of joules can be converted into joules by dividing by 4.18 or by multiplying by 0.239.