We propose a new tool – the aRithmetic Discourse Profile (RDP) for analyzing the arithmetic discourse of students, based on the commognitive theory. The tool maps students’ discourse on a continuum between ritual and explorative participation. We apply the tool to the discourse of 12 7th grade students and exemplify the analysis on three tasks: one in addition of whole numbers, one in multiplication and one with fractions. Tasks were taken from regular curricular materials of elementary school mathematics. We discuss the affordances of the tool in relation to existing diagnostic tools.