The invention relates to an apparatus for ballast weighing on a crane, comprising at least two ballasting cylinders that are equipped to lift/lower the ballast and that each comprise at least one pressure transducer in the region of the piston and/or rod side, and comprising at least one evaluation unit that is equipped to calculate the mass moved by the ballasting cylinders from the pressures detected by the pressure transducers on retraction and/or extension of the ballasting cylinders, excluding the friction forces occurring in the ballasting cylinders. The invention furthermore is directed to a method for calculating the ballast weight of a crane by means of a corresponding apparatus.