The aim of this study was to compare four tools for calculation of nitrous oxide (N₂O) emissions under the renewable energy directive. All the tools follow the methodology of the international panel on climate change. The first calculations of N₂O fluxes were based on the Tier 1 method using the BioGrace tool. The second and the third ones followed the Tier 2 methodology, applying the global nitrous oxide calculator and the Lesschen emission factors, respectively. The last assessment was performed in accordance with the Tier 3 approach by using the denitrification-decomposition model. The N₂O fluxes were calculated for rapeseed cultivation in a 4-year crop rotation in Poland. The same input data were applied in all methods. The average of N₂O emissions varied in the range of 1.99-3.78 kg N₂O ha^-1 y^-1, depending on the approach used (Lesschen emission factors > denitrification-decomposition > global nitrous oxide calculator > BioGrace). This paper illustrates that, at country level, the Lesschen emission factors method worked as well as the denitrification-decomposition model for Poland. The advantage of this approach is the simplicity of collecting the necessary data, in contrast to process-based modelling. Moreover, the Tier 2 method provides mitigation measures similar to the denitrification-decomposition model, related to crop type, climatic conditions, and management practices.