The present invention relates to an apparatus for determining a pedal displacement of a brake pedal for a vehicle brake system. In said case, a magnetic element disposed on a piston in the interior of a housing of a brake cylinder is used, which cooperates with a sensor element disposed at the outside of the brake cylinder in order to detect positions and movements of the piston. As positions and movements of the piston connected to the magnetic element correspond directly with positions and movements of a brake pedal connected rigidly and directly thereto or characterize said positions and movements in the case of an indirect connection to the brake pedal, it is possible on the basis of positions and movements, which are determined for the piston, to infer the underlying pedal displacement of the brake pedal.