Calorific value indicates the amount of heat available from a fuel.The greater the calorific value of fuel, the larger is its ability to produce heat. In case of solid and liquid fuels, the calorific value is expressed in cal/gm or kcal/kg. However , in case of gaseous fuels, it is generally stated in cal/litre or kcal/litre. Below is given a table of various types of fuels and calorific value along with composition.
| S.No. | Particular | Calorific Value | Composition |
| 1. | Solid Fuels | | |
| (1) Lignite | 5,000 Kcal/kg | C=67%, H=5%, O=20%, ash=8% | |
| (2) Bituminous coal | 7,600 kcal/kg | C=83%, H=5.5%, O=5%, ash=6.5% | |
| (3) Anthracite coal | 8500 kcal/kg | C=90%, H=3%, O=2%, ash=5% | |
| 2. | Liquid Fuel | | |
| (1) Heavy oil | 11,000 kcal/kg | C=86%, H=12%, S=2% | |
| (2) Diesel oil | 11,000 kcal/kg | C=86.3%, H=12.8%, S=0.9% | |
| (3) Petrol | 11,100 kcal/kg | C=86%, H=14% | |
| 3. | Gasoline Fuel | | |
| (1) Natural gas | 530 kcal/m3 | CH4=84%,C2H6=10% Other hydrocarbons=5% | |
| (2) Coal gas | 7600 kcal/m3 | CH4=35%, H=45%, CO=8%, N=6% CO2=2%, other hydrocarbons=4% |