Biogas calculator is a tool used to estimate the volume of biogas production, production of electricity and heat, project implementation costs, as well as the payback period of incurred investment costs. The analysis consists of four stages in which it is possible to insert the input data and the results of the analysis are generated. The first one concerns the dosing of substrates. The second presents the parameters of the biogas plant operation, the effects of the fermentation process and the volume of electricity and heat production. The third stage is used to introduce unit prices of revenues, as well as define the parameters of the heating network. The fourth step presents the results of financial simulation.