Accumix™ is a lyophilized 7-peptide standard that provides broad mass-range coverage for both tuning and calibration of ion trap (i.e. Finnigan LCQ- and LTQ-MS) and Fourier transform mass spectrometers. Direct infusion of the Accumix peptide standard produces 9 major parent ions that span the mass range of m/z 285 to 1580. Broad range mass coverage permits tuning of the mass spectrometer across its entire dynamic range. The exact masses provided for each ion also permit simple and regular broad range mass calibration of Fourier transform mass spectrometers for maintenance of high-mass accuracy measurement operating conditions.