This paper provides criteria for selections of life cycle inventory data through analyzing some products in Taiwan. Customized assessment software tool was also built to help the designer assessing carbon footprint for these products. By studying the global warming potential item in life cycle inventory and impact assessment software and databases such as: ecoinvent, JEMAI LCA Pro, SimaPro, VHK, and Gabi, this research can provide those who have many software or databases with data priority and criteria. For those companies or user with only one set of software or database, this research also provide a data substitution method to help completing the assessment process. Finally, suggestions are also made to improve inventory analysis. This research can assist the medium/small sized private enterprises in Taiwan with their product carbon footprint assessment needs.