This bachelor thesis consists of the theoretical and experimental part. In chapter vegetable oils is showed the definition and classification of vegetable oils and biodiesel and their application as biofuels. Also the economic and environmental need for this fuel were elaborated throughout history to the present day. In the introductory part of the chapter three, entitled as a “Calorimetry” is defined the procedure for determining the calorific value by a calorimeter. The second part of this chapter closely describes the experimental procedure on a Parr model 1341 Oxygen Bomb Calorimeter used for the purposes of this bachelor thesis. The upper specific combustion heat value of the four samples (sunflower, olive, sesame oil and biodiesel) was determined experimentally in the three measurements and the mean value for each sample has been calculated. All the results and the calculation procedures are transparently presented and the obtained specific combustion heat values of the all samples are analysed and compared with each other. In the final part of this bachelor thesis, described and compared are the advantages and disadvantages of the biofuels in the relation to the conventional fossil fuels on the basis of the obtained results. It is explained in detail and argued why the vegetable oils have the potential for wider application and how it is possible to extract the best from biofuels with the minimal negative impact on the population and the nature in general.