Anyone who counts calories has already miscalculated

1 calorie (cal) is defined as the amount of energy required to heat 1 g of water from 14.5 to 15.5 °C. The name derives from the Latin term calor for heat. The conversion to the SI unit joule is done with a fixed factor: 1 cal = 4.187 J. The calorific value of food is given in kilojoules (kJ); 1 kilocalorie (kcal) logically corresponds to 4.187 kJ.