Operating method for a roll train having a plurality of roll stands (1 to 4) for rolling a metal strip, - wherein the roll stands (1 to 4) - in relation to a respective roll stand (1 to 4) - are sometimes operated in a normal operation and sometimes operated in a calibration operation, - wherein work rolls of the respective roll stand (1 to 4) are set to a roll gap (s1 to S4) such that the work rolls roll the metal strip during normal operation by virtue of setting a control element position (p1 to p4) of a control element (10 to 14) of the respective roll stand (1 to 4), - wherein a calibration value (sC1 to sC4) of the respective roll stand (1 to 4), further state parameters (P1 to P4) of the respective roll stand (1 to 4) and a setpoint roll gap (s1* to s4*) to be set are predetermined for a model describing the respective roll stand (1 to 4) for the purposes of establishing the control element position to be set (p1 to p4) and the model establishes the control element position (p1 to p4) to be set on the basis of the calibration value (sC1 to sC4), the further state parameters (P1 to P4) and the setpoint roll gap (s1* to s4*), - wherein the calibration value of the respective roll stand (1 to 4) is established during the calibration operation and this is followed by a transition from the calibration operation to the normal operation and - wherein the calibration value (sC1 to sC4) established in the calibration operation is used during the normal operation for establishing the control element position (p1 to p4) to be set as calibration value (sC1 to sC4) of the respective roll stand (1 to 4), characterized - in that the control element position (p1 to p4) is initially set during the calibration operation in such a way that the metal strip passes through the roll stand (1 to 4) without being rolled by the work rolls, - in that the control element position (p1 to p4) is thereupon varied during the calibration operation such that the work rolls roll the metal strip, - in that a thickness (d) of the metal strip is captured during the calibration operation by means of a thickness measuring device disposed downstream of the respective roll stand (1 to 4), the thickness being that with which the metal strip runs out of the respective roll stand (1 to 4), and - in that the thickness (d), the further state parameters (P1 to P4) and the control element position (p1 to p4) are supplied to the model and the model establishes the calibration value (sC1 to sC4) of the respective roll stand on the basis of the thickness (d), the further state parameters (P1 to P4) and the control element position (p1 to p4). - wherein the roll stands (1 to 4) - in relation to a respective roll stand (1 to 4) - are sometimes operated in a normal operation and sometimes operated in a calibration operation, - wherein work rolls of the respective roll stand (1 to 4) are set to a roll gap (s1 to S4) such that the work rolls roll the metal strip during normal operation by virtue of setting a control element position (p1 to p4) of a control element (10 to 14) of the respective roll stand (1 to 4), - wherein a calibration value (sC1 to sC4) of the respective roll stand (1 to 4), further state parameters (P1 to P4) of the respective roll stand (1 to 4) and a setpoint roll gap (s1* to s4*) to be set are predetermined for a model describing the respective roll stand (1 to 4) for the purposes of establishing the control element position to be set (p1 to p4) and the model establishes the control element position (p1 to p4) to be set on the basis of the calibration value (sC1 to sC4), the further state parameters (P1 to P4) and the setpoint roll gap (s1* to s4*), - wherein the calibration value of the respective roll stand (1 to 4) is established during the calibration operation and this is followed by a transition from the calibration operation to the normal operation and - wherein the calibration value (sC1 to sC4) established in the calibration operation is used during the normal operation for establishing the control element position (p1 to p4) to be set as calibration value (sC1 to sC4) of the respective roll stand (1 to 4), characterized - in that the control element position (p1 to p4) is initially set during the calibration operation in such a way that the metal strip passes through the roll stand (1 to 4) without being rolled by the work rolls, - in that the control element position (p1 to p4) is thereupon varied during the calibration operation such that the work rolls roll the metal strip, - in that a thickness (d) of the metal strip is captured during the calibration operation by means of a thickness measuring device disposed downstream of the respective roll stand (1 to 4), the thickness being that with which the metal strip runs out of the respective roll stand (1 to 4), and - in that the thickness (d), the further state parameters (P1 to P4) and the control element position (p1 to p4) are supplied to the model and the model establishes the calibration value (sC1 to sC4) of the respective roll stand on the basis of the thickness (d), the further state parameters (P1 to P4) and the control element position (p1 to p4).