A classical test for accessing the potential creativity of an individual is based on ideational fluency, where a person is asked to generate all possible uses for a familiar item like a piece of paper. In scoring the results, it is intuitive that the suggested uses should not be weighted equally. Those suggested in radically different categories are 'worth more'; than those suggested within the same category only. We used information theory to derive a simple mathematical expression for a more objective measure of ideational fluency. We call this the creativity quotient (CQ). This innovative measure was examined using a small sample of participants, and is illustrated by the responses of two typical individuals from an ideational fluency task. The CQ accounts for the number of ideas (fluency), plus the number of categories (flexibility). Ongoing research will examine the independence of CQ from established measures of intelligence and personality.