Abstract. A conversion process is often carried out to migrate data during BIM and GIS integration, often from the highly detailed BIM to the less detailed GIS environment. Due to the differences between the two systems, information loss occurs during conversion. While research has been focusing on addressing information loss on the semantics, it is also necessary to quantify geometric changes resulted from converting geometry representations used in the two systems. This paper describes a preliminary study which evaluates the geometric changes during conversion for a list of primitives. The outcome shows that the metrics are useful both to those carrying out the conversion to balance between potential information loss and resulting data complexity, and to end users of the converted information to assess the fitness for purpose and impact of the conversion results.