In the case of a method for measuring the geometry of a drilled hole in a workpiece, a measuring system is used which has a measuring unit with a measuring mandrel that can be moved bidirectionally along a travel path parallel to a measuring mandrel axis. The measuring mandrel is calibrated at least once with the use of a reference device by way of at least one reference element. During a measuring operation, the reference device is arranged in a neutral location outside the travel path of the measuring mandrel in such a way that the measuring mandrel can be introduced into the drilled hole without dipping through the reference element. To carry out a calibration operation, the reference device is moved out of the neutral location. The measuring mandrel is moved into a calibrating location, where a measurement for calibrating the measuring mandrel is carried out.