Enthalpy of formation for organic compounds is suppositional, because formation reaction for most of organic compound are assumed. For example, carbon and hydrogen does not directly react (like hydrogen and oxygen) to form methane, ethane or most other hydrocarbons. Therefore, direct estimation of enthalpy of formation is difficult for such reactions.
However, we can assume standard enthapy of formation by measuring standard enthalpy of combustion using calorimeter. This calculator is calculating standard enthalpy of formation from elemetal composition and lower heating value of organic compounds. The standard reference state is taken as 298K temperature and 1 atm pressure.
For using this calculator insert elemental composition of organic compound by mass as percentage in fields of carbon, hydrogen, sulphar, oxygen and other matter. Remember that this calculator considers amount of compound as 1 kg. If there is uncombustable matter in compound like moisture, ash or nitrogen include it in total mass of compound for calculating mass fractions of compound's elements. Please note that summation of fuel elements must be 100. Accuracy of calculation largely depends on data entered. For better accuracy use of practically measured data is recommanded.