It is of paramount importance to determine the lightship characteristics of a newly built vessel correctly. Conventionally, an inclining experiment is performed after the ship is launched in order to determine the lightship GM and in turn KG values. However, there has been an ongoing debate about the validity of the results since it bears some assumptions during the test and calculation procedure. Although the inclining experiment is mandatory by the Intact Stability Code of International Maritime Organization, there emerged various alternative methods recently claiming to reveal better results. In this study, an uncertainty analysis has been carried out on GM and KG values of various sample vessels. Based on the results on the uncertainty analysis, a cumulative margin of error from various sources has been determined within a specified confidence level. Finally, the outcome for the sample vessels was detailed and evaluated in reference to that of the actual inclining experiment reports.