This paper deals with experimental forecast of real GDP growth of the Czech economy in 2020 that is in period significantly affected by the global Covid-19 pandemics. Our prediction was created by applying set of loss functions related to past forecasts of public institutions (Ministry of finance, Czech national bank) onto their pre-coronavirus summer 2019 forecast. Results create range of potential output growth, whose mean value implies real GDP decrease by about one-tenth in current year. Although the method is rather simple, it (based on current information) indicates that economic activity might decrease notably more, than predicted by the mentioned public bodies.