Before starting NDA preparation, every aspirant must know the eligibility rules first. 1. Age Limit Candidates must be 16.5 to 19.5 years old on the specified exam date — even a few days' gap can disqualify you. 2. Educational Qualification Army wing: 12th pass, any stream Air Force/Naval wing: 12th with Physics & Maths compulsory This is why many students start NDA-focused prep from 11th itself, so their subjects match the wing they want. 3. Marital Status Only unmarried candidates, maintained till training completion. 4. Nationality Indian citizens, with limited exceptions for Nepal/Bhutan subjects and Tibetan refugees. 5. Physical Standards Height: ~157 cm minimum (relaxations for Gorkhas, hill/NE states) Weight: Proportionate to height & age Vision: Stricter for Air Force Full medical exam after written test and SSB 6. Attempts No fixed cap — age limit naturally restricts most to 2–3 attempts. Why This Matters Many aspirants prepare without confirming eligibility first — especially the Physics/Maths rule for Air Force/Navy. Knowing this early helps choose the right stream from 11th and avoid last-minute surprises.