Combined defense service (CDS) is the name of an examination conducted by UPSC, giving youths to join defense services in another way apart from the National Defense Academy (NDA) exam. If you want to be a part of forces as an Officer, and tried your luck in the NDA exam, but got unsuccessful, not to worry as you can still join the tri-services through CDS examination.

CDS Exam complete Details
CDS Exam Complete Details

CDS is an entrance exam to join defense service and other exams through which you can make your career in forces are AFCAT, NDA. CDS exam is conducted by UPSC twice in a year for admission in the academies of tri-services:

Indian naval academy  @ Ezhimala, Kerala,

Indian Military Academy @ Dehradun, Uttrakhand,

Officers’ Training Academy @ Chennai, and to

Air Force Academy @ Hyderabad

Here through this exam, Candidates are joined in Officer Cadre in the armed forces, and the exam formality like notification, conducting written exam, and preparing the final merit list is undertaken by UPSC. The exam is conducted twice in a year and termed as CDS 1 & CDS 2.

  • CDS 1 – is conducted in the month of February
  • CDS 2 – is conducted in the month of November
  • CDS is a written exam after which candidates are shortlisted for SSB interviews to be held at different SSB centers across the country.
  • There are no limits of attempts for the CDS Exam until your age limit exceeds, so you can try your luck as many times you want, providing your age allows you to sit in the exam.

If the aspirants will complete their graduation by the anticipated time, they can apply for the exam.

Both men and women can apply for this examination.

CDS Examination Process
CDS Examination Process

Eligibility Criteria for CDS Exam:

Eligibility Criteria for this examination is divided into four sections and those are Nationality, Age, Marital Status, and Gender.

Age Limits, Sex, and Marital Status :

As per the declaration of UPSC, the candidates need to be unmarried and should not be a widower or should not be a divorcee ( except OTA entry). You can go through all details depicted in the table below:

AFA19-23UM IF <25 YEARS162.5
OTA (M)19-25UM157
OTA (W)19-25UM,

Individuals from Gorkha and NE states including Garhwali and Kumaon, the Minimum height requirement will be 5 cms less, while for individuals from Lakshadweep it is relaxed by 2 cms.

Nationality : 

Candidate must be meeting one of the following criteria of nationality to be eligible in appearing for CDS exam:

  1.  A Citizen of India,
  2. A subject of Bhutan,
  3. A subject of Nepal,
  4. A Tibetan refugee who came over to India before January 1962 with the intention of permanently settling in India,
  5. A person of Indian origin who has migrated from Pakistan, Burma, Sri Lanka and East African Countries of Kenya, Uganda, the United Republic of Tanzania, Zambia, Malawi, Zaire, and Ethiopia or Vietnam with the intention of permanently settling in India

 Educational Qualification: 

You must be having your Bachelor’s degree for applying in the exam, or else must be appearing in the final year of degree so that, at the time of the interview you can produce a certificate of passing the degree exam.

For I.M.A. and OTA, — Degree of a university or equivalent degree recognized by Central/State Government. 

For INA( Indian Naval Academy) — Degree in Engineering from a recognized University/institution. 

For Air Force Academy — Degree of a recognized university( with Physics and Mathematics at 10+2) or a Bachelor’s degree in Engineering. 

Note: Candidates in the final year of their eligible degree will need to show the proof of passing the qualifying exam by a date to be specified in the notification. 

Physical Standards for Male and Female: 

Candidates must be physically and mentally fit as per the guidelines of UPSC notifications. It is advised to undertake a thorough medical examination prior to applying to this examination, as medically unfit candidates are not encouraged to take part in the process. Most commonly found medical defects are :

Candidates with diseases or symptoms of a disease like Piles, Overweight or Underweight, Wax in Ears, Hydrocele / Varicocele / Phimosis, Deviated Nasal Septum, Flat feet, Swetting in Feet, Color Blindness, Ankle lock, Hypertension, Tuberculosis, or evidence of tuberculosis, lesions of lungs, heart, musculoskeletal lesions of the chest wall are subject to reject.

Tattoos in any form on the body are not permitted except inner face part of the forearm, however, any candidate from a specific tribe can be allowed with tattoos on body parts but it must be cross-checked.

CDS Examination in Detail

How to Apply for CDS 

  • Nowadays, the process of application very simple and is purely online and it can be filled by visiting the official website of UPSC on

Step 1: Registration of candidature on the website

Step 2: Pay CDS Application Fee which is 200/- and can be paid online by any available gateway on the website or by offline through Challan or at the bank. Candidates belonging to reserve categories are exempted from paying this Application fees.

Part 3: Fill the CDS Application Form

While steps 1 & 2 are a subpart of part 1 of UPSC registration, filling the application form is part 2 of the registration process. After completion of payment details, the individual has to fill application form like personal details, qualification, experience, choice of exam centre etc. Once filled and submitted, there is no scope for correction in the application form, so care must be taken while filling the application form.

Step 4: Upload CDS Photo, Signature 


CDS : Syllabus and Exam Pattern

Syllabus and exam pattern is different for each academy i.e IMA, OTA etc. Candidate giving exam for OTA have 4 hours of exam with 200 marks while candidates for IMA, INA, IFA have to appear in the written exam lasts for 6 hours for 300 marks.

CDS Syllabus: 

Mainly CDS exam for IMA, IFA & INA consists of General Knowledge, English Language, and Elementary Mathematics. Further mathematics part is divided into Geometry, Statistics, Arithmetic Ability, Trigonometry, Algebra, Mensuration, and Numbers System.

For OTA candidates there are only two sections which are General Knowledge & English Language.

You must be sure while answering each question as each wrong answer carries a negative marking of 0.33 marks.

A. English Subject: Usage of words, Grammar, Vocabulary, Antonyms & Synonyms, Parts of Speech, Direct & Indirect Speech, Idioms & Phrases, Active & Passive Voice, Ordering of words in a sentence, Spotting Errors, etc. 

B. General Knowledge Subject: Indian History, Indian Geography, Current Events (National & International), Indian Culture & Heritage, Indian Economy, General Politics, Indian Constitution, Biology, Statement true/false, Physics, Chemistry, Defence-related, Environment, Current Awareness, Sociology, Award, Sport, Book,

C. Mathematics Subject :

i) Arithmetic Ability: Number System, Fundamental operations, Unitary method, time and distance, time and work, percentages, applications to simple and compound interest, profit and loss, ratio and proportion, variation, Elementary Number Theory, Division algorithm, Prime and composite numbers, Tests of divisibility, Factorization Theorem, H.C.F. and L.C.M, Euclidean algorithm, Logarithms

ii) Algebra: Basic Operations, simple factors, Remainder Theorem, H.C.F. & L.C.M., Theory of polynomials, Solutions of quadratic equations, analytical and graphical solutions, Simultaneous linear inequations, Practical problems – simultaneous, linear equations or inequations, Rational expressions, conditional identities, Laws of indices

iii) Trigonometry: Simple cases of heights and distances, Use of trigonometric tables, Simple trigonometric identities, Sine ×, cosine ×, Tangent × when 0° < × < 90° Values of sin ×, cos ×, and tan ×, for × = 0°, 30°, 45°, 60°, and 90°

iv) Mensuration: Areas of squares, rectangles, parallelograms, triangle, and circle, Areas of figures, Surface area and volume of cuboids, lateral surface and volume of right circular cones and cylinders, surface area and volume of spheres.

v) Geometry: Lines and angles, Plane and plane figures,

vi) Theorems on: Properties of angles at a point, Parallel lines, Sides and angles of a triangle, Congruency of triangles, Similar triangle, Circles and its properties including tangents and normal’s,  Loci, The concurrence of medians and altitudes, Properties of angles, sides & diagonals of a parallelogram, rectangle, and square.

vii) Statistics: Collection and tabulation of statistical data, Graphical representation frequency polygons, histograms, bar charts, pie charts, etc.

viii) Measures of central tendency.

ix) Numbers System: Natural numbers, Integers, Rational and Real numbers

CDS Exam Pattern and Marking Scheme

Exam Pattern for INA, IMA, and AFA: 

1202 HOURS100

CDS Exam Pattern for OTA (officer’ Training Academy):


CDS Exam: Marking Scheme:

The marking scheme is different for each section and In both sections, English and General Awareness weightage of every right answer is +0.83 and for every wrong answer, it is -0.27. In the Mathematics section, candidates will be credited with +1 marks for every correct answer and will be deducted – 0.33 for each wrong attempt. 

CDS Selection Procedure: 

Individuals who declared pass in the written exam by UPSC will be shortlisted for another stage of the recruitment and that is interview or SSB (Service Selection Board).

  • Stage I of SSB verifies the OLQ in the candidates by some simple tests like Intelligence Rating with Picture Perception and Description Test (PP&DT)
  • Stage II contains tests like Psychological Test, Interview, Group Testing Office Task, and Conference. 
  • You can go through each detail about the procedure of SSB by clicking another blog on 10 tips and tricks to clear SSB successfully.

 Being a Candidate, you can opt for a change of dates in the SSB interview if you are not able to attend SSB on the designated dates but make sure that authority must be satisfied with your reason to amend the date. So if possible your request for postponement of your SSB interview must be supported by relevant documents

Document Verification is another stage after the SSB interview where all your documents are cross-checked for authenticity and eligibility. So you must carry important documents like Qualification Certificates, Proof of Identity( PAN, Aadhar, Voter Card), Birth Certificate, Passport-size Photograph, Category Certificate if belong to Reserve category and Residence Proof with you while going for attending SSB.

Final Merit list will be prepared by UPSC and can be checked by visiting official website.

Recommended Books for CDS Exam : 

Some of the recommended books listed here but with these books online exams, the market search can be useful.

ENGLISHa) Wren & Martin’s
High School English Grammar & Composition
b) Word Power Made Easy
c) Objective General English

MATHEMATICSa) Quantitative Aptitude for Competitive Examination
b) Mathematics for CDS Examination
by R S Aggarwal
a) General Knowledge
(Latest Edition)
b) Manorama Year Book
c) Daily News Paper
Arihant Publication

CDS 2021: Preparation Tips:

Every candidate has their own method of preparation and rules. But there are few things those should be kept in mind while you are preparing for CDS Exam:

i) Be confident

ii) Don’t follow any study material Blindly

iii) Check the syllabus in detail first

iv) Check the exam pattern by which you will come to know which subject has higher weightage and will help you to decide which subject to give more attention.

v) Start preparing for the exam well before the exam at least 5 to 6 months prior to exam dates.

vi) Schedule is more important in preparation so follow it religiously

vii) Follow the daily newspaper and only limited pages out of newspaper should be for use and rest all to be ignored.

viii) Mock test and interviews will be of another help

ix) Previous years question papers solving technique will always provide you an extra edge among others.

x) Attending SSB coaching can be of help by which you will come to know the sequence of events, you are going to expose within SSB.

xi) Don’t get confused by talking with anyone unnecessary on your preparation.