A method is proposed for comparing configurations of complex machines based on the design features that affect the relative geometric positions of functional elements. Complexity is defined as the level of difficulty associated with securing functional elements relative to one another. The evaluation method focuses on the major components of complexity that govern the relative positions of critical functional elements—connection system error, linear dimension variation and form error. Using the method, the complexity arising from various design decisions is clearly identified by complexity factors obtained for each contributor to positional error in the critical geometric relationships in a machine. It is intended that these simple measures of complexity will be applied at the configuration design stage of the product development process to identify areas of weakness and to enable the selection of the least complex configuration.