The soil erodibility factor according to the USLE method was calculated for selected Polish soils. Data from 10 experimental plots of different soils in black fallow a terrain slope of 10% and in sprinkling conditions, were used for the study. The comparison of real data and data obtained form equations given by Wischmeier and Smith, as well as by Wiliams, revealed considerable differences in K_USLE values of the investigated soils. The statistical investigations were conducted to find the best fitting between observed and numerically predicted K_USLE values. The highest correlation (R=0.65) revealed the pair of M_USLE and ln(K_d/K_w) variables, where K_d represents real K_USLE values, while K_w K_USLE was calculated with Williams equation. The non-linear logarithmic regression model has shown the best fit, reaching the regression of R=0.77 between variables ln(K_d/K_w), M_USLE and outflow coefficient.