The calorific value, or CV, of a fuel represents the amount of heat produced by its combustion. Calorific value is a function of the energy densities of the gases or other substances that compose the fuel being measured. Calorific values of fuels are often described in terms of kilowatt hours, abbreviated "kWh," or Joules, abbreviated "J." The calorific value of a substance is used to determine the amount of energy created when using that substance as fuel. By researching the energy density of a substance, you can easily calculate the calorific value, in calories, of a fuel using a single computation.

Determine the energy density of the fuel being measured. Energy densities of various fuels can be found online at scientific research institutions, such as the University of Washington School of Oceanography. For an example, we will calculate the calorific value of diesel fuel. The University of Washington lists the energy density of diesel fuel as 36.4 MegaJoules per litre, or 36.4 MJ/L.

Convert the energy density from MegaJoules per litre to Joules per litre by multiplying the value by 1 million. A single Megajoule is equal to 1 million Joules; therefore you can convert a value from MegaJoules to Joules by multiplying that number by 1 million Joules / 1 Megajoule. In our example, diesel fuel has an energy density of 36.4 million MegaJoules per litre.

Calculate the calorific value by dividing the energy density found in Step 2 by 4.184. A single calorie is equal to approximately 4.184 Joules. To convert an energy density described in terms of Joules per litre into the calorific value, you must multiply the energy density by 1 calorie / 4.184 Joules. Dividing the energy density by 4.184 Joules, in our example, we find that the calorific value of diesel fuel is about 8.7 million calories per litre.