Calorific value and kcal (or kilocalories) are related but different concepts. Calorific value is a measure of the amount of heat released by a fuel when it is burned and is typically expressed in units of energy per unit of mass, such as joules per kilogram (J/kg) or kilocalories per kilogram (kcal/kg).

On the other hand, a kilocalorie is a unit of energy equal to 1,000 calories, and is commonly used to express the energy content of food. For example, when you see the label on a food product that says it contains 100 kcal, it means that consuming that food will provide your body with 100,000 calories of energy.

In other words, calorific value is a measure of the energy content of a fuel, while kcal is a unit of energy used to express the energy content of food.