On this page
Many science students in Class 11 and 12 hear about the National Defence Academy (NDA) only as "the defence exam" and are not sure what it tests or whether their PCM preparation counts. It counts a great deal. This post goes through what UPSC's own notice says about the papers, eligibility and marking, works two typical questions, and ends with a practice routine.
All facts below come from the UPSC notice for the NDA and NA Examination (II), 2026. UPSC publishes a fresh notice for each sitting, so check the current one on upsc.gov.in before you plan around any date or rule.
Who can take the NDA exam?
The 2026 (II) notice allowed only unmarried male and female candidates born between 1 January 2008 and 1 January 2011. The 2026 (I) notice, dated 10 December 2025, used a window six months earlier: born between 1 July 2007 and 1 July 2010. So the age rule moves with each sitting. The education rule depends on the wing:
Army wing of NDA: Class 12 pass under the 10+2 pattern, any stream.
Air Force and Navy wings of NDA, and the 10+2 Cadet Entry Scheme at the Indian Naval Academy: Class 12 pass with Physics, Chemistry and Mathematics.
Students still appearing in Class 12 can apply.
That notice listed about 394 vacancies across the Army, Navy, Air Force and Naval Academy, with separate vacancies for women in each service. The 2026 (II) written exam was held on 13 September 2026.
What is in the two written papers?
The written exam has two papers, each 2½ hours long, and all questions are objective:
Paper I, Mathematics (300 marks): algebra, matrices and determinants, trigonometry, two- and three-dimensional geometry, differential calculus, integral calculus and differential equations, vectors, and statistics and probability. This is close to the Class 11 and 12 maths you already study.
Paper II, General Ability Test (600 marks): Part A is English (200 marks). Part B is General Knowledge (400 marks), covering physics, chemistry, general science, history, geography and current events.
The note under the syllabus gives the approximate weight of each Part B section: physics 25%, chemistry 15%, general science 10%, history 20%, geography 20% and current events 10%. For a science student that is useful arithmetic. Physics is worth about 100 marks, chemistry about 60 and general science about 40, so roughly half of Part B is science. The physics list is school level: density and Archimedes' principle, Newton's laws, heat, sound, reflection and refraction, magnets, Ohm's law and simple circuits.
Candidates who pass the written exam go to a Services Selection Board (SSB) interview worth 900 marks, held in two stages over several days. Calculators and log tables are not allowed in the written papers.
How does the negative marking work?
The notice says each question has four alternatives, and a wrong answer costs one third of that question's marks. A blank answer costs nothing, and marking two answers counts as wrong.
Worked example. Call the marks for one question m.
Pure guess among four options. Expected score = (1/4)m − (3/4)(m/3) = m/4 − m/4 = 0. On average, blind guessing neither gains nor loses.
You can rule out one option. Expected score = (1/3)m − (2/3)(m/3) = m/3 − 2m/9 = m/9. Now a guess is worth taking.
You can rule out two options. Expected score = (1/2)m − (1/2)(m/3) = m/2 − m/6 = m/3.
So the rule is simple: guess only when you can eliminate at least one option with a real reason. Our post on negative marking and when to guess goes deeper into this.
A typical maths question, worked
Heights and distances appear in the trigonometry unit of Paper I.
Example. From a point on level ground 20 m from the foot of a tower, the angle of elevation of the top is 60°. Find the height.
Draw the right triangle: base 20 m, angle 60° at the observer, height h opposite that angle.
tan 60° = h / 20, and tan 60° = √3.
h = 20√3 ≈ 20 × 1.732 = 34.64 m.
Because there is no calculator, learn the exact values of sin, cos and tan at 30°, 45° and 60°, and √2 ≈ 1.414 and √3 ≈ 1.732. Our guide to trigonometric identities practice helps here.
What are the common mistakes?
Treating Paper II as "only GK". Half of Part B is school science, and English is a third of the paper. Both reward steady practice.
Ignoring probability and statistics. They are a full unit in Paper I. Our post on probability mistakes covers the usual traps.
Slow arithmetic. Without a calculator, a JEE-style approach of long algebra can run out the clock. Practise mental arithmetic and estimation.
Guessing everything. As the worked example shows, blind guessing has zero expected value and adds risk.
A practice routine for the next eight weeks
Weeks 1 to 2: read the full syllabus in the notice and mark each topic as done, weak or new.
Weeks 3 to 6: four maths sessions a week (one unit at a time, then mixed sets), two sessions of Part B science, and one English session with reading and grammar.
Weeks 7 to 8: timed 2½-hour papers from UPSC's previous question papers, scored with the one-third penalty, then an error log by topic.
If you get stuck on why a method works, the Fermi Problem Library has a step-by-step solver that explains the reasoning, which helps you check a solution you could not finish.
Today, download the current NDA notice from upsc.gov.in and mark the topics in Paper I that you have not yet studied.
