Increasing demands for quality control, both in production as well as in R&D, have resulted the proliferation of instrument measurement calibration. However, despite the fact that vacuum measurement is often made with significantly larger uncertainties and errors than other physical or thermodynamic quantities, the calibration of vacuum measurement instrumentation, in particular in the high vacuum range, is generally ignored or neglected. Objective practical difficulties have been identified and defined which make vacuum measurement calibration problematic and very often not practically feasible. The requirements for vacuum measurement uncertainties for most practical vacuum systems have been assessed. In an effort to make reproducible vacuum measurement more accessible, a more practical approach to vacuum measurement calibration has been defined and developed. The approach incorporates a vacuum calibration system, whose specifications and design satisfy the accuracy requirements for all but the most demanding users of vacuum technology. Calibration results are presented which provide justification for the approach. In addition the new approach defines a concept of Specific Reference Calibration, SRC. SRC does not necessarily provide calibration of the users vacuum measurement instruments. However SRC does enable practically defining and attaining reproducible vacuum process conditions in the users vacuum system, with significant advantages over conventional calibration. The new approach is aimed to overcome the difficulties, which have inhibited the proliferation of vacuum measurement calibration up to this time, and to facilitate the attainment of reproducible vacuum conditions and processes.