This paper proposes a new measure of skills mismatch that combines information about skill proficiency, self-reported mismatch and skill use. The theoretical foundations underling this measure allow identifying minimum and maximum skill requirements for each occupation and to classify workers into three groups, the well-matched, the under-skilled and the over-skilled. The availability of skill use data further permit the computation of the degree of under and overusage of skills in the economy. The empirical analysis is carried out using the first wave of the OECD Survey of Adult Skills (PIAAC) and the findings are compared across skill domains, labour market status and countries.