Generic Risk Matrices. Risk matrices are tools for qualitative estimation and risk ranking. Risk matrices comprise a square divided into a number of boxes, with each box representing a different underlying estimation of risk. Typically three to five (possibly more) categories are used for the possible consequences and a similar number for the possible likelihoods. Each risk box in the matrix represents the combination of a particular level of likelihood and consequence, and can be assigned either a numerical or descriptive risk value (the risk estimate).