Abstract: A method for adapting the volume of a collar bag (1) that is partially filled with bulk material, whereby the collar (3) of said bag is formed by two opposite-lying outwardly bent edge strips (5) and two opposite-lying inwardly bent second edge strips (7), to the volume of the bulk material contained in said bag (1). The invention is characterized in that the first edge strips (5) are pulled apart, whereby the wall of the bag is drawn out of the upper unfilled part of the bag over the folded edges (6) and into the collar (3) or the cross-section of the bag is reduced by pressing the opposite-lying larger parts of the wall. The invention also relates to the collar bag (1) and the device to carry out the above-mentioned method.