1 calorie equals approximately 4.186 kilojoules. Both calories and kilojoules are units of heat, and a calorie is a kilocalorie. 1 kilojoule is 1,000 joules. A calorie is one calorie, and 1,000 calories is one kilocalorie. The conversion factor between calories and joules is 4.186. 1 calorie is equal to 4.186 kilojoules. A kilojoule is a unit of heat, and a kilojoule is one thousand joules. Nowadays, kilojoules are commonly used to measure the amount of calories contained in food and the amount of calories burned per unit of time for a certain kind of exercise. People generally control their weight by controlling the amount of calories consumed in food and the amount of calories burned in exercise. People who need to control their energy intake are advised to consult a professional nutritionist.