A method for operating a measuring site (1), wherein a measured variable is determined by a sensor (5) that can be calibrated and in which an exact as possible planning of activities, to which, for example, calibration or sensor replacement belong, is possible is obtained, in accordance with the method, in that the sensor (5) is calibrated at presettable calibration points in time, that at least one parameter in conjunction with calibration is stored as a part of reference data of the sensor (5) and that at least one aging-dependent variable of a sensor (8, 6) differing from the sensor (5) is estimated based on reference data of the sensor (5).