A rotor balancing method for a gas turbine, the method comprising: providing a rotor comprising: a first bearing and a second bearing , and a plurality of correction planes comprising a first correction plane and a second correction plane , wherein a first balancing weight (W1) is attached to the first correction plane and remains attached for all following influence runs; performing a first influence run by: running the rotor at an intended balance speed and recording a first set of vibration measurements at the first bearing and the second bearing , wherein the vibrations detected at the first bearing have a smaller magnitude than the vibrations detected at the second bearing ; fitting a first calibration weight (M1) to the second correction plane ; performing a second influence run by: running the rotor at the intended balance speed and recording a second set of vibration measurements at the first bearing and the second bearing , and removing the first calibration weight (M1) from the rotor ; calculating an influence vector of the second correction plane using the first set of vibration measurements and the second set of vibration measurements; carrying out balancing of the rotor by: fitting a final balancing weight (W1') to the first correction plane , and fitting a second balancing weight (W2) to the second correction plane using the calculated influence vector, characterised by providing a data set comprising a reference influence vector of the second correction plane , wherein the reference influence vector is an influence vector of a reference rotor of the same production type as the rotor ; using a reference influence vector of the second correction plane to determine the mass and the angular location of the first calibration weight (M1), wherein the mass of the first calibration weight (M1) is inversely proportional to the magnitude of the reference influence vector of the second correction plane . providing a rotor comprising: a first bearing and a second bearing , and a plurality of correction planes comprising a first correction plane and a second correction plane , wherein a first balancing weight (W1) is attached to the first correction plane and remains attached for all following influence runs; performing a first influence run by: running the rotor at an intended balance speed and recording a first set of vibration measurements at the first bearing and the second bearing , wherein the vibrations detected at the first bearing have a smaller magnitude than the vibrations detected at the second bearing ; fitting a first calibration weight (M1) to the second correction plane ; performing a second influence run by: running the rotor at the intended balance speed and recording a second set of vibration measurements at the first bearing and the second bearing , and removing the first calibration weight (M1) from the rotor ; calculating an influence vector of the second correction plane using the first set of vibration measurements and the second set of vibration measurements; carrying out balancing of the rotor by: fitting a final balancing weight (W1') to the first correction plane , and fitting a second balancing weight (W2) to the second correction plane using the calculated influence vector, characterised by providing a data set comprising a reference influence vector of the second correction plane , wherein the reference influence vector is an influence vector of a reference rotor of the same production type as the rotor ; using a reference influence vector of the second correction plane to determine the mass and the angular location of the first calibration weight (M1), wherein the mass of the first calibration weight (M1) is inversely proportional to the magnitude of the reference influence vector of the second correction plane . <EOS>