A method of detecting an overall dimension of a plate-shaped workpiece to be processed on a processing machine by a contactless-acting sensor includes moving the workpiece by a motion device of the processing machine in a predetermined direction until the sensor detects a first workpiece edge by a first change of state, detecting a first position of the workpiece where the first change of state happens by an evaluation device connected to the sensor, moving the workpiece by the motion device in a direction toward a second workpiece edge until the sensor detects the second workpiece edge by a second change of state, detecting a second position of the workpiece where the second change of state happens by the evaluation device, and determining an overall dimension of the workpiece by a determination of a distance between the first position and the second position of the workpiece.