Ontologies are conceptual models of particular domains, and domains can be modeled differently, representing different opinions, beliefs or perspectives. In other terms, ontologies may disagree with some particular pieces of information and among themselves. Assessing such agreements and disagreements is very useful in a variety of scenarios, in particular when integrating external elements of information into existing ones. In this paper, we present a set of measures to evaluate the agreement and disagreement of an ontology with a statement or with other ontologies. While our work goes beyond the naive approach of checking for logical inconsistencies, it relies on a complete formal framework based on the semantics of the considered ontologies. The experiments realized on several concrete scenarios show the validity of our approach and the usefulness of measuring agreement and disagreement in ontologies.