Correction factors that relate the dry mass of food items consumed by brown bears (Ursus arctos) to the volume of the corresponding residue in the feces have been determined for various foods consumed by brown bears in North America, but the values of some important foods used by European populations remain unknown. We estimated the correction factors for wild cherries (Prunus avium), beechnuts (Fagus sylvatica), hazelnuts (Corylus avellana), and supplemental foods (corn, oats, and sugar beets) provided to bears in many areas of Europe. In 2011, we fed captive bears from the Warsaw Municipal Zoological Garden, Poland, with known amounts of these foods and measured the volume of their remains in their feces. Overall, correction factors for supplemental foods were lower than for natural foods. We recommend use of the values estimated in this study and further evaluations of correction factors for bear food items not yet assessed.