EN
Paper presents the calculation of production costs per milk unit depending on cows' milking performance for the years 1997-2001. The calculation took into consideration 5 options of milk production costs, i.e. from 2 to 6 K dm³. On the basis of calculation the unit cost functions were approximated depending on the individual performance. Analyzing the function variability curve the optimum production relative to unit costs was identified. Milk performance levels, at which the minimum values for the analyzed unit cost functions during the period of the study was obtained, amounted ca. 6.5 K and 7 K dm³ and was beyond the function's domain. The unit cost functions generated during the study were used for calculation of the flexibility ratio that defines the change of cost depending on changes in individual milk performance of the cows. Finally, the net pro fit was calculated. It increased with the increase of milk performance within the range of from 2 to 6 K dm³.