The format of the main examination in the UPSC Civil Services exam consists of nine papers, out of which two are qualifying papers in Indian languages and English. The remaining papers include four General Studies papers, one Essay paper, and two optional subject papers. Each paper is scored out of 250 marks, contributing to a total of 1750 marks for the Mains. The exam focuses on assessing a candidate's analytical capabilities, depth of knowledge, and understanding of contemporary issues.