Scientific and social discourse examines primarily the environmental performance of large enterprise actors. Although these large enterprises usually operate on an international level, over half of the added value created in the European Union and thus over half of the environmental damage are generated by small- and medium-sized enterprises (SME). Nevertheless, while the tools and expertise required to measure environmental performance are available for large enterprises, the SME sector has only limited access to these tools. s part of our research, we have developed an ecological footprint (EF) calculator applicable to the specificities of the SME sector, which has been tested on six Hungarian companies operating in different sectors and organisational frameworks. The test results indicate that the managerial information system of partnerships includes all the main inputs that are necessary to estimate a company’s EF. However, in the case of sole proprietorships, most of the required data can only be acquired by estimation. Our EF calculations on analysed firms cannot be considered as representative data. But on the base of the case studies, we can suggest that our EF calculator for SMEs is suitable to take a more comprehensive survey on EF of Hungarian and international firms, in order to generate sectoral benchmarks. Ecological footprint among analysed enterprises ranged between 5102 and 263,589 global square metres. It is caused mainly by (1) the sector (e.g. constructions have generally larger footprints than office activities) and (2) the size, expressed in number of employees or value added. To increase transparency of the environmental performance of the SME sector, we recommend that the supplementary annex of partnerships includes the main input data necessary for the calculation of the EF in a comparable and consistent way, in natural units of measurement. With such information and our calculator, it would be possible to determine the average environmental impact of the individual sectors, which would provide an appropriate starting point for the environmental investments of enterprises.