ABSTRACT: This article deals with the question of how the protagonists of the first Mexican Constitution integrated the need for an electoral census into that nation’s fundamental chart (1824). Here, “political arithmetic” is defined as a crucial calculus in order to obtain a basis of representation in political powers. The article points out the necessity of further investigating the circulation among the elites of symbols by which the relationship between population and territory was understood in modern political terms. It lines out how the necessary data for this calculus, of heterogeneous origin, were adapted to the modern basic category of the subject, and how that data was applied in public debate. Finally, it traces the role of the data in the constitutional process between 1820 and 1824.