Ecological footprint calculation methodology is generally well defined on a national scale. It is also proposed by several authors as a corporate sustainability metric, yet for this scale, there is no consensus method. The aim of this paper is to identify the consequences of such methodological liberties within the ecological footprint estimation and its use as a decision aid tool on the scale of a public organization. The method was developed and validated for the Vanoise National Park which undertook to reduce its ecological footprint by 10% between 2009 and 2007. The methodological liberties inherent to ecological footprint analysis on an organization scale generate methodological choices that may influence the results in terms of environmental impact hierarchy and priority of actions. Therefore, such analysis requires transparency in the methodological choices behind the calculation and the involvement of the end-users in these choices.