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UPSC Prelims has 1/3 negative marking, for every wrong answer, one-third of the question’s marks are deducted. So a 2-mark question wrongly answered loses 0.66 marks. Use the free calculator below to find your exact prelims score.
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The UPSC Civil Services Preliminary Examination is the first hurdle of the CSE, and it is built to reward accuracy over volume. Both papers — General Studies Paper I and the CSAT (Paper II) — are objective, and both apply the same one-third penalty for wrong answers. Because Prelims is purely a screening stage and the marks do not carry forward to the final ranking, a single careless guess can be the difference between qualifying for the Mains and sitting out an entire attempt. Understanding exactly how the deduction is computed is therefore not a formality; it is part of your exam strategy.
GS Paper I has 100 questions worth 2 marks each, for a maximum of 200 marks. CSAT has 80 questions worth 2.5 marks each, for a maximum of 200 marks, and is qualifying in nature (you need 33% to clear it). The negative marking rule is identical in structure across both papers, so the calculator above lets you switch the question count and instantly model either paper.
For every wrong answer, UPSC deducts one-third of the marks assigned to that question. Since a GS Paper I question is worth 2 marks, a wrong answer costs you 0.66 marks — not 0.33. This is the single most misunderstood point about UPSC negative marking: the penalty is one-third of the question’s marks, not a flat one-third of a mark. Questions you leave unattempted carry no penalty at all, which is why blind guessing is rarely worth it.
Suppose you attempt 90 of the 100 questions in GS Paper I, getting 70 correct and 20 wrong, and leave 10 blank.
Marks for correct: 70 × 2 = 140. Penalty for wrong: 20 × 0.66 = 13.33. Final score: 140 − 13.33.
Your net score is 126.67 out of 200.
The number that actually matters is not how many questions you attempted but your strike rate— the share of your attempts that were correct. In the example above, 70 correct out of 90 attempted is a 78% strike rate, and even with 20 wrong answers the candidate keeps almost 127 marks. Now compare a candidate who attempts all 100 questions but is only 60% accurate: 60 correct (120 marks) and 40 wrong (−26.4) leaves just 93.6 marks. Attempting more questions actively hurt them.
As a rule of thumb, only convert a guess into an attempt when you can confidently eliminate at least two of the four options. With one-third negative marking, a pure four-option guess has an expected value close to zero, but a two-option educated guess tilts the odds in your favour. Track your sectional accuracy across mock tests rather than your raw attempt count — that is the metric that predicts whether you clear the cutoff.
The Prelims cutoff is not fixed; it moves each year with the difficulty of the paper and the number of vacancies, typically settling somewhere between 90 and 100 marks in GS Paper I. Because you cannot know the exact cutoff in advance, the safe strategy is to build a margin through accuracy rather than chasing a high gross score through volume. A candidate who locks in 95 clean marks with disciplined attempting is far more secure than one who reaches 110 gross but bleeds it back through twenty wrong answers. Use the calculator above after every mock to see your net score, and treat any paper where negative marking erases more than ten marks as a signal to tighten your attempting, not to study harder.
Yes. CSAT applies the same one-third negative marking as GS Paper I. Each wrong answer deducts one-third of that question’s marks. CSAT is qualifying, so you only need 33% to clear it, but the penalty still applies to every wrong answer.
For GS Paper I, where each question is worth 2 marks, a wrong answer deducts 0.66 marks (one-third of 2). The deduction is always one-third of the marks for that specific question, not a flat value.
No. Questions you leave blank carry zero marks and no penalty. Negative marking applies only to questions you answer incorrectly.
Only when you can eliminate at least two of the four options. A pure random guess has roughly zero expected value under one-third negative marking, but an educated guess between two remaining options gives you a positive expected return.
No. Prelims is only a screening test. Your final rank is decided by the Mains and the Personality Test. Prelims marks are not added to the final tally, but you must clear the Prelims cutoff to proceed.