In this article, some existing error estimation methods are presented and their suitability for modern software development projects is analyzed. Based on this analysis, a new software error estimation method SEEC (Software Error Estimation by Component-wise comparison), specifically designed for multi-site, multi-component software projects, is introduced. The required activities and the mathematical formulation of the new method are presented. Finally, the integration of the SEEC method to a software development process is illustrated with the SPEM process modeling language.