What is the difference between kJ and kcal (and Calorie)

Kilojoules (kJ), and calories (kcal), are both units that measure energy. Our program uses kcal to measure your energy intake and energy used. If you would prefer, you can convert kcals to kJs by multiplying by 4.18 (100 kcals = 418 kJ).
A kilocalorie is the amount of heat required to raise the temperature of 1 kilogram of water by one degree Celsius. The ““calorie”” we refer to in food is actually kilocalorie. One (1) kilocalorie is the same as one (1) Calorie (upper case C).