What is the full structure and purpose of the three stages in the UPSC Civil Services Examination?

The UPSC Civil Services Examination (CSE) is a year-long, three-stage selection process designed to recruit officers for India’s premier administrative services, such as the Indian Administrative Service (IAS) and Indian Police Service (IPS).

Stage 1: Preliminary Examination (Prelims)
Structure: Consists of two objective-type papers (MCQs) conducted on a single day:
General Studies (GS) Paper I: 100 questions (200 marks) covering history, geography, polity, and current affairs.
Civil Services Aptitude Test (CSAT) Paper II: 80 questions (200 marks) testing reasoning, analytical skills, and basic numeracy.
Purpose: Serves as a screening test to filter out the majority of candidates. Only Paper I marks determine the merit for the next stage, while CSAT is qualifying (requires a minimum of 33% or 66.67 marks). Marks from Prelims are not counted in the final ranking. 

Stage 2: Main Examination (Mains)
Structure: A descriptive written examination consisting of nine papers typically held over 5–7 days:
Qualifying Papers: Indian Language and English (300 marks each; marks are not counted for merit).
Merit-Ranking Papers: One Essay, four General Studies (GS I–IV), and two papers on one Optional Subject (250 marks each; total 1750 marks).
Purpose: Evaluates a candidate’s intellectual depth, analytical thinking, and clarity of expression. It moves beyond rote memory to test the ability to articulate complex ideas coherently. 

Stage 3: Personality Test (Interview)
Structure: A 20–30 minute conversation with an impartial board of experts at the UPSC headquarters in New Delhi, carrying 275 marks.
Purpose: Assesses the candidate’s suitability for a career in public service. It focuses on mental alertness, critical assimilation, leadership qualities, and intellectual and moral integrity rather than academic knowledge alone. 

Final Selection: The final merit list is based on the combined score of the Mains (1750)