The aim of this paper is to compare different methods of rain factor calculation. In this research were used two methodologies i.e. Wischmeier–Smith [1978] methodology and Hudson’s [1971] methodology. The main difference between these two methodologies is in the data processing especially in the calculation and choosing of kinetic energy intervals. These factors influence the resultant values of rain factor. The data for this research were provided by Slovak Hydrometeorological Institute in Bratislava, concretely were prepared data from rain-guage station Sereď for period 1962–1966. Obtained and calculated values show that Hudson relations and consequence resultant values are lower than the values calculated with Wischmeier–Smith’s methodology. After these calculations were resultant values of rain factor compared with existing values of rain factor calculated in the past by Soil Science and Conservation research Institute in the map form. This comparison showed that values calculated with using Hudson’s methodology are closer to past values. This fact is significant because it will be useful to revaluate the used methodology also because that there are deficient data about rain and the Hudson’s methodology can be use also for deficient data.

21-27