This document constitutes the final report of the project Improvement of the SAUNA Noble Gas System Calibration Procedures performed under a CTBTO contract. In this report we present the outcome of the studies performed to increase the understanding of the different steps in the SAUNA detector calibration process and the associated errors, as well as recommendations for improvements to the calibration procedures. The report includes: A summary of referenced physical constants used in the SAUNA calibration procedures. Studies and recommendations for updates of the gamma and beta detector energy and resolution calibration procedures. This includes a study of the position dependence of the gamma calibration and studies of simulated data to evaluate the unfolding of the beta resolution from the two-dimensional betagamma spectrum. Studies and recommendations for updates of the detector efficiency calibration procedure. Studies of the inter-isotope interference factors and possible updates to include additional interference factors.