Determining lot sizes in production areas is an essential task of production planning and control. Due to the growing number of product variants, calculating economical lot sizes is becoming increasingly important in the industrial practice. Although planning lot sizes plays an important role in industrial production, existing methods only partially consider the variety of impacts. This paper presents existing methods and discusses their impact on the multi-criteria objective achievement of industrial companies. Based on actual case studies the logistical and economical relevance of determining lot sizes is illustrated and the suitability of different approaches for industrial practice is discussed.