Calibration function for time of flight mass spectrometers with extreme mass accuracy

The invention relates to methods for converting time-of-flight values of ion signals into mass values in time-of-flight mass spectrometers capable of extreme mass accuracy. The invention provides a calibration function for time--of-flight mass spectrometers where not only the time of flight of a specific ionic species is used in the conversion into masses, but also the number of ions which fly together through the mass spectrometer in each case. In time-of-flight mass spectrometers designed to measure the masses of the ions with an extreme mass accuracy far better than one part per million, unexpected effects occur which resemble a delaying "traffic jam" of the ions (or the electrons in the multiplier) that is dependent on the number of ions of one species on their flight through the mass spectrometer.